feat(sme): add basic SME tests

This test enters streaming mode and iterates through supported SME
vector lengths to ensure that EL3 has properly enabled SME for use at
lower non-secure ELs. If FA64 is present, it attempts to execute an
illegal instruction.

Signed-off-by: John Powell <john.powell@arm.com>
Change-Id: Ic80a1e5652a88261524778329d3bc99901a799d8
9 files changed