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

arch/arm64/kvm/hyp/entry.S

@@ -171,7 +171,7 @@ alternative_else
 	dsb	sy		// Synchronize against in-flight ld/st
 	isb			// Prevent an early read of side-effect free ISR
 	mrs	x2, isr_el1
-	tbnz	x2, #8, 2f	// ISR_EL1.A
+	tbnz	x2, #ISR_EL1_A_SHIFT, 2f
 	ret
 	nop
 2: