KVM: arm64: Do not transfer page refcount for THP adjustment

GUP affects a refcount common to all pages forming the THP. There is
therefore no need to move the refcount from a tail to the head page.
Under the hood it decrements and increments the same counter.

Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20230928173205.2826598-2-vdonnefort@google.com


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