KVM: arm64: Hoist PAuth checks into KVM_ARM_VCPU_INIT ioctl

Test for feature support in the ioctl handler rather than
kvm_reset_vcpu(). Continue to uphold our all-or-nothing policy with
address and generic pointer authentication.

Link: https://lore.kernel.org/r/20230920195036.1169791-5-oliver.upton@linux.dev


Signed-off-by: Oliver Upton <oliver.upton@linux.dev>