Makefile: Add FEAT_RNG support define

Define ENABLE_FEAT_RNG that describes whether the
armv8.5 FEAT_RNG is supported in this build. This
allows conditional inclusion of code targetting
RNDR and RNDRRS registers.

Signed-off-by: Tomas Pilar <tomas@nuviainc.com>
Change-Id: Idd632f8b9bc20ea3d8793f55ead88fa12cb08821
1 file changed