Create a new "memmap" target for the Makefile, which prints a
representation of the memory map for the build. The information are
extracted from the .map files by the "print_memory_map.py" tools.

Change-Id: Id5ebc7ce8a3a571c7ac4848be14657cf2fd711f4
Signed-off-by: Louis Mayencourt <louis.mayencourt@arm.com>