Remove useless copies of meminfo structures

Platform setup code has to reserve some memory for storing the
memory layout information.  It is populated in early platform setup
code.

blx_get_sec_mem_layout() functions used to return a copy of this
structure.  This patch modifies blx_get_sec_mem_layout() functions
so that they now directly return a pointer to their memory layout
structure.  It ensures that the memory layout returned by
blx_get_sec_mem_layout() is always up-to-date and also avoids a
useless copy of the meminfo structure.

Also rename blx_get_sec_mem_layout() to blx_plat_sec_mem_layout()
to make it clear those functions are platform specific.

Change-Id: Ic7a6f9d6b6236b14865ab48a9f5eff545ce56551
diff --git a/include/bl2.h b/include/bl2.h
index 3981a86..e105641 100644
--- a/include/bl2.h
+++ b/include/bl2.h
@@ -42,7 +42,7 @@
  * Function prototypes
  *****************************************/
 extern void bl2_platform_setup(void);
-extern meminfo bl2_get_sec_mem_layout(void);
+extern meminfo *bl2_plat_sec_mem_layout(void);
 extern meminfo bl2_get_ns_mem_layout(void);
 
 #endif /* __BL2_H__ */