build(bl31): add symbols for memory layout

Add symbols for mapping the physical memory layout of BL31. There are
symbols that partially satisfy this requirement, however, the naming of
these is inconsistent.

Signed-off-by: Harrison Mutai <harrison.mutai@arm.com>
Change-Id: I413cc4e9d7471582eed61d631bed6214bd17a564
1 file changed