refactor(build): absorb CFLAGS into TF_CFLAGS

CFLAGS is the standard and expected variable for passing flags to the
compiler. The build system also uses TF_CFLAGS to define its own flags.
But the build rules need to specify both. So append CFLAGS to TF_CFLAGS
so that only the latter needs to be passed.

Change-Id: I4abb6c9dfc252a805063691e8a100f0ec0c785ad
Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>
2 files changed