platform: msm_shared: Add support for finding DDR size

Add support to find DDR size for any device at run time and add macros
to define ddr types suppoprted.

Change-Id: I262de16efa85f42441c5231ebacc59baf31bfa23
diff --git a/platform/msm_shared/include/mmu.h b/platform/msm_shared/include/mmu.h
index d70872e..9154066 100644
--- a/platform/msm_shared/include/mmu.h
+++ b/platform/msm_shared/include/mmu.h
@@ -32,6 +32,9 @@
 #include <sys/types.h>
 #include <arch/arm/mmu.h>
 
+#define MEM_4GB      0x100000000
+#define MEM_3GB      0xC0000000
+
 #ifdef LPAE
 typedef struct {
 	uint64_t paddress;