KVM: arm64: Use symbolic definition for ISR_EL1.A

Now that we are generating ISR_EL1 we have acquired a constant for
ISR_EL1.A, use it rather than the magic number we had been using in the KVM
entry code.

Suggested-by: Marc Zyngier <maz@kernel.org>
Acked-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20221208-arm64-isr-el1-v2-3-89f7073a1ca9@kernel.org


Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>