Fix a false fail for SMC WORKAROUND2 test on Cortex-A76

Some platforms with A76 core do not require the dynamic
mitigation using SMCCC_ARCH_WORKAROUND_2 call. Test which
verifies such workaround can be skipped in such scenario.

Signed-off-by: Madhukar Pappireddy <madhukar.pappireddy@arm.com>
Change-Id: Iacf27da7181828a2fd1166bd6eeb069ba27da0c5