arm64: Rename WORKAROUND_1319367 to SPECULATIVE_AT_NVHE

To match SPECULATIVE_AT_VHE let's also have a generic name for the NVHE
variant.

Acked-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Steven Price <steven.price@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>