fix(build): allow lower address access with gcc-12

fix(build): allow lower address access with gcc-12

With gcc-12 any lower address access can trigger a warning/error
this would be useful in other parts of system but in TF-A
there are various reasons to access to the lower address ranges,
example using mmio_read_*/writes_*

So setup to allow access to lower addresses while using gcc-12

Change-Id: Id1b4012b13bc6876d83b90a347fee12478a1921d
Signed-off-by: Govindraj Raja <govindraj.raja@arm.com>