fix(zynqmp): conditional reservation of memory in DTB

When the TF-A is placed in DDR memory range, the DDR memory range is
getting explicitly reserved in the default device tree by TF-A.
This creates an error condition in the use case where Device tree is
not present or it is present at a different location.

To fix this, a new build time parameter, XILINX_OF_BOARD_DTB_ADDR, is
introduced. The TF-A will reserve the DDR memory only when a valid
DTB address is provided to XILINX_OF_BOARD_DTB_ADDR during build.

Now the user has options, either manually reserve the desired
DDR address range for TF-A in device tree or let TF-A access and modify
the device tree, to reserve the DDR address range, in runtime using
the build parameter.

Change-Id: I846fa373ba9f7c984eda3a55ccaaa622082cad81
Signed-off-by: Akshay Belsare <akshay.belsare@amd.com>
diff --git a/plat/xilinx/zynqmp/bl31_zynqmp_setup.c b/plat/xilinx/zynqmp/bl31_zynqmp_setup.c
index 1d963e8..0ebd088 100644
--- a/plat/xilinx/zynqmp/bl31_zynqmp_setup.c
+++ b/plat/xilinx/zynqmp/bl31_zynqmp_setup.c
@@ -171,7 +171,7 @@
 }
 #endif
 
-#if (BL31_LIMIT < PLAT_DDR_LOWMEM_MAX)
+#if (defined(XILINX_OF_BOARD_DTB_ADDR) && !IS_TFA_IN_OCM(BL31_BASE))
 static void prepare_dtb(void)
 {
 	void *dtb = (void *)XILINX_OF_BOARD_DTB_ADDR;
@@ -217,7 +217,7 @@
 
 void bl31_platform_setup(void)
 {
-#if (BL31_LIMIT < PLAT_DDR_LOWMEM_MAX)
+#if (defined(XILINX_OF_BOARD_DTB_ADDR) && !IS_TFA_IN_OCM(BL31_BASE))
 	prepare_dtb();
 #endif
 
@@ -250,7 +250,7 @@
 	plat_arm_interconnect_enter_coherency();
 
 	const mmap_region_t bl_regions[] = {
-#if (BL31_LIMIT < PLAT_DDR_LOWMEM_MAX)
+#if (defined(XILINX_OF_BOARD_DTB_ADDR) && !IS_TFA_IN_OCM(BL31_BASE))
 		MAP_REGION_FLAT(XILINX_OF_BOARD_DTB_ADDR, XILINX_OF_BOARD_DTB_MAX_SIZE,
 			MT_MEMORY | MT_RW | MT_NS),
 #endif