KVM: arm64: Condition HW AF updates on config option

As it currently stands, KVM makes use of FEAT_HAFDBS unconditionally.
Use of the feature in the rest of the kernel is guarded by an associated
Kconfig option.

Align KVM with the rest of the kernel and only enable VTCR_HA when
ARM64_HW_AFDBM is enabled. This can be helpful for testing changes to
the stage-2 access fault path on Armv8.1+ implementations.

Link: https://lore.kernel.org/r/20221202185156.696189-7-oliver.upton@linux.dev


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