arm64: Make use of ARCH_WORKAROUND_1 even when KVM is not enabled

We seem to be pretending that we don't have any firmware mitigation
when KVM is not compiled in, which is not quite expected.

Bring back the mitigation in this case.

Fixes: 4db61fef ("arm64: kvm: Modernize __smccc_workaround_1_smc_start annotations")
Cc: <stable@vger.kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Will Deacon <will@kernel.org>