fix(fvp): permit enabling SME for SPD=spmd

Essentially revert [1] to permit specifying SME support along with
SPD=spmd on FVP platform.

[1] https://review.trustedfirmware.org/c/TF-A/trusted-firmware-a/+/20764

Signed-off-by: Olivier Deprez <olivier.deprez@arm.com>
Change-Id: Iab15d5a4c966b9f5b265ccde6711765e242abeaa
1 file changed