Kconfig: Unify endian support option

Move SUPPORT_BIG_ENDIAN, SUPPORT_LITTLE_ENDIAN to top-level
arch Kconfig and let architectures select them as necessary.

Remove if guard for Endianness selection choice so we can
have one of SYS_BIG_ENDIAN, SYS_LITTLE_ENDIAN config symbol
defined even on single endian system.

Default endian to SYS_BIG_ENDIAN for MIPS || MICROBLAZE
and LITTLE_ENDIAN for the rest to retain old config
behaviour.

Note: PPC, SH, Xtensa are technically bi-endian, but I
checked compiled u-boot image with readelf, U-Boot currently
only support little endian for SH and Xtensa, Big Endian for
PPC.

Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index eb7f3ad..38577af 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -28,14 +28,14 @@
 	select OF_ISA_BUS
 	select PCI_MAP_SYSTEM_MEMORY
 	select ROM_EXCEPTION_VECTORS
-	select SUPPORTS_BIG_ENDIAN
 	select SUPPORTS_CPU_MIPS32_R1
 	select SUPPORTS_CPU_MIPS32_R2
 	select SUPPORTS_CPU_MIPS32_R6
 	select SUPPORTS_CPU_MIPS64_R1
 	select SUPPORTS_CPU_MIPS64_R2
 	select SUPPORTS_CPU_MIPS64_R6
-	select SUPPORTS_LITTLE_ENDIAN
+	select SUPPORT_BIG_ENDIAN
+	select SUPPORT_LITTLE_ENDIAN
 	select SWAP_IO_SPACE
 	imply CMD_DM
 
@@ -86,7 +86,7 @@
 	select ROM_EXCEPTION_VECTORS
 	select SUPPORTS_CPU_MIPS32_R1
 	select SUPPORTS_CPU_MIPS32_R2
-	select SUPPORTS_LITTLE_ENDIAN
+	select SUPPORT_LITTLE_ENDIAN
 	select SUPPORT_SPL
 
 config ARCH_JZ47XX
@@ -112,7 +112,7 @@
 	select MIPS_TUNE_OCTEON3
 	select MTD
 	select ROM_EXCEPTION_VECTORS
-	select SUPPORTS_BIG_ENDIAN
+	select SUPPORT_BIG_ENDIAN
 	select SUPPORTS_CPU_MIPS64_OCTEON
 	select PHYS_64BIT
 	select OF_CONTROL
@@ -138,14 +138,14 @@
 	select OF_BOARD_SETUP
 	select OF_CONTROL
 	select ROM_EXCEPTION_VECTORS
-	select SUPPORTS_BIG_ENDIAN
 	select SUPPORTS_CPU_MIPS32_R1
 	select SUPPORTS_CPU_MIPS32_R2
 	select SUPPORTS_CPU_MIPS32_R6
 	select SUPPORTS_CPU_MIPS64_R1
 	select SUPPORTS_CPU_MIPS64_R2
 	select SUPPORTS_CPU_MIPS64_R6
-	select SUPPORTS_LITTLE_ENDIAN
+	select SUPPORT_BIG_ENDIAN
+	select SUPPORT_LITTLE_ENDIAN
 	imply CMD_DM
 
 config TARGET_XILFPGA
@@ -159,7 +159,7 @@
 	select ROM_EXCEPTION_VECTORS
 	select SUPPORTS_CPU_MIPS32_R1
 	select SUPPORTS_CPU_MIPS32_R2
-	select SUPPORTS_LITTLE_ENDIAN
+	select SUPPORT_LITTLE_ENDIAN
 	imply CMD_DM
 	help
 	  This supports IMGTEC MIPSfpga platform
@@ -413,12 +413,6 @@
 
 endmenu
 
-config SUPPORTS_BIG_ENDIAN
-	bool
-
-config SUPPORTS_LITTLE_ENDIAN
-	bool
-
 config SUPPORTS_CPU_MIPS32_R1
 	bool