arm64: kvm: Replace hardcoded '1' with SYS_PAR_EL1_F

Now that we have a definition for the 'F' field of PAR_EL1, use that
instead of coding the immediate directly.

Acked-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will@kernel.org>