zynqmp: Do not place u-boot to reserved memory location

TF-A and SecureOS can allocate the part of DDR for self but U-Boot is not
handling this configuration that the part of memory is reserved and
shouldn't be used by U-Boot. That's why read all reserved memory locations
and don't use it.
The code was taken from commit 4a1b975dac02 ("board: stm32mp1: reserve
memory for OP-TEE in device tree") and commit 1419e5b5167e ("stm32mp:
update MMU config before the relocation") which is used by stm32 and does
the job properly.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/board/xilinx/zynqmp/zynqmp.c b/board/xilinx/zynqmp/zynqmp.c
index 208eade..7177c5a 100644
--- a/board/xilinx/zynqmp/zynqmp.c
+++ b/board/xilinx/zynqmp/zynqmp.c
@@ -11,6 +11,8 @@
 #include <env.h>
 #include <env_internal.h>
 #include <init.h>
+#include <image.h>
+#include <lmb.h>
 #include <log.h>
 #include <net.h>
 #include <sata.h>
@@ -453,6 +455,25 @@
 
 	return 0;
 }
+
+ulong board_get_usable_ram_top(ulong total_size)
+{
+	phys_size_t size;
+	phys_addr_t reg;
+	struct lmb lmb;
+
+	/* found enough not-reserved memory to relocated U-Boot */
+	lmb_init(&lmb);
+	lmb_add(&lmb, gd->ram_base, gd->ram_size);
+	boot_fdt_add_mem_rsv_regions(&lmb, (void *)gd->fdt_blob);
+	size = ALIGN(CONFIG_SYS_MALLOC_LEN + total_size, MMU_SECTION_SIZE),
+	reg = lmb_alloc(&lmb, size, MMU_SECTION_SIZE);
+
+	if (!reg)
+		reg = gd->ram_top - size;
+
+	return reg + size;
+}
 #else
 int dram_init_banksize(void)
 {