PSCI: Fix MISRA defects in MEM_PROTECT ...

MISRA C-2012 Rules 10.1 and 10.3.

Change-Id: I88cd5f56cda5780f2e0ba541c0f5b561309ab3af
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

mem_protect: Add mem_protect API ...

This patch adds the generic code that links the psci smc handler
with the platform function that implements the mem_protect and
mem_check_range functionalities. These functions are  optional
APIs added in PSCI v1.1 (ARM DEN022D).

Change-Id: I3bac1307a5ce2c7a196ace76db8317e8d8c8bb3f
Signed-off-by: Roberto Vargas <roberto.vargas@arm.com>