fdt: Implement weak arch_fixup_fdt()

Only ARM and in some configs MIPS really implement arch_fixup_fdt().
Others just use the same boilerplate which is not good by itself,
but what's worse if we try to build with disabled CONFIG_CMD_BOOTM
and enabled CONFIG_OF_LIBFDT we'll hit an unknown symbol which was
apparently implemented in arch/xxx/lib/bootm.c.

Now with weak arch_fixup_fdt() right in image-fdt.c where it is
used we get both items highlighted above fixed.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Cc: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
Cc: Simon Glass <sjg@chromium.org>
Cc: York Sun <york.sun@nxp.com>
Cc: Stefan Roese <sr@denx.de>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>
diff --git a/arch/arc/lib/bootm.c b/arch/arc/lib/bootm.c
index 9eef707..4d4acff 100644
--- a/arch/arc/lib/bootm.c
+++ b/arch/arc/lib/bootm.c
@@ -37,11 +37,6 @@
 	lmb_reserve(lmb, sp, (CONFIG_SYS_SDRAM_BASE + gd->ram_size - sp));
 }
 
-int arch_fixup_fdt(void *blob)
-{
-	return 0;
-}
-
 static int cleanup_before_linux(void)
 {
 	disable_interrupts();
diff --git a/arch/microblaze/lib/bootm.c b/arch/microblaze/lib/bootm.c
index 93525cc..154671d 100644
--- a/arch/microblaze/lib/bootm.c
+++ b/arch/microblaze/lib/bootm.c
@@ -17,11 +17,6 @@
 
 DECLARE_GLOBAL_DATA_PTR;
 
-int arch_fixup_fdt(void *blob)
-{
-	return 0;
-}
-
 int do_bootm_linux(int flag, int argc, char * const argv[],
 		   bootm_headers_t *images)
 {
diff --git a/arch/mips/lib/bootm.c b/arch/mips/lib/bootm.c
index 5a9a281..9dc4740 100644
--- a/arch/mips/lib/bootm.c
+++ b/arch/mips/lib/bootm.c
@@ -253,17 +253,15 @@
 #endif
 }
 
+#if CONFIG_IS_ENABLED(MIPS_BOOT_FDT) && CONFIG_IS_ENABLED(OF_LIBFDT)
 int arch_fixup_fdt(void *blob)
 {
-#if CONFIG_IS_ENABLED(MIPS_BOOT_FDT) && CONFIG_IS_ENABLED(OF_LIBFDT)
 	u64 mem_start = virt_to_phys((void *)gd->bd->bi_memstart);
 	u64 mem_size = gd->ram_size;
 
 	return fdt_fixup_memory_banks(blob, &mem_start, &mem_size, 1);
-#else
-	return 0;
-#endif
 }
+#endif
 
 static int boot_setup_fdt(bootm_headers_t *images)
 {
diff --git a/arch/nds32/lib/bootm.c b/arch/nds32/lib/bootm.c
index 42b15df..0d7f578 100644
--- a/arch/nds32/lib/bootm.c
+++ b/arch/nds32/lib/bootm.c
@@ -15,12 +15,6 @@
 
 DECLARE_GLOBAL_DATA_PTR;
 
-int arch_fixup_fdt(void *blob)
-{
-	return 0;
-}
-
-
 #if defined(CONFIG_SETUP_MEMORY_TAGS) || \
 	defined(CONFIG_CMDLINE_TAG) || \
 	defined(CONFIG_INITRD_TAG) || \
diff --git a/arch/powerpc/lib/bootm.c b/arch/powerpc/lib/bootm.c
index b9ae24d..6ef644d 100644
--- a/arch/powerpc/lib/bootm.c
+++ b/arch/powerpc/lib/bootm.c
@@ -40,11 +40,6 @@
 #define CONFIG_SYS_LINUX_LOWMEM_MAX_SIZE	(768*1024*1024)
 #endif
 
-int arch_fixup_fdt(void *blob)
-{
-	return 0;
-}
-
 static void boot_jump_linux(bootm_headers_t *images)
 {
 	void	(*kernel)(bd_t *, ulong r4, ulong r5, ulong r6,
diff --git a/arch/sandbox/lib/bootm.c b/arch/sandbox/lib/bootm.c
index 4cdd18f..0c9a797 100644
--- a/arch/sandbox/lib/bootm.c
+++ b/arch/sandbox/lib/bootm.c
@@ -50,11 +50,6 @@
 	return ret;
 }
 
-int arch_fixup_fdt(void *blob)
-{
-	return 0;
-}
-
 int do_bootm_linux(int flag, int argc, char *argv[], bootm_headers_t *images)
 {
 	if (flag & (BOOTM_STATE_OS_GO | BOOTM_STATE_OS_FAKE_GO)) {
diff --git a/arch/x86/lib/bootm.c b/arch/x86/lib/bootm.c
index e548cdb..8e76ba3 100644
--- a/arch/x86/lib/bootm.c
+++ b/arch/x86/lib/bootm.c
@@ -28,11 +28,6 @@
 
 #define COMMAND_LINE_OFFSET 0x9000
 
-int arch_fixup_fdt(void *blob)
-{
-	return 0;
-}
-
 __weak void board_quiesce_devices(void)
 {
 }
diff --git a/common/image-fdt.c b/common/image-fdt.c
index 1e94646..24e4c7c 100644
--- a/common/image-fdt.c
+++ b/common/image-fdt.c
@@ -454,6 +454,11 @@
 	return 1;
 }
 
+__weak int arch_fixup_fdt(void *blob)
+{
+	return 0;
+}
+
 int image_setup_libfdt(bootm_headers_t *images, void *blob,
 		       int of_size, struct lmb *lmb)
 {