Fix -Werror related build issues

The release build triggers unused variable warnings due to asserts
being removed. Change affected code to remove the warnings.
For projects depending on the TF-A external component define the
TF-A specific ENABLE_ASSERTIONS=0 macro to avoid warnings in TF-A
source files.

Signed-off-by: Gabor Toth <gabor.toth2@arm.com>
Change-Id: Idf861bb1c7b1f90fc3a0d10aa59ea1e5943ea49a
3 files changed