Remove SMCCC 2.0 support

SMCCC v2.0 is no longer required for SPM, and won't be needed in the
future.

The SPM implementation based on SPCI and SPRT was using it, but it has
been adapted to SMCCC v1.0.

Change-Id: I624b32f9547274b50add4ea81b485cc9f5121e53
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>
3 files changed