ANDROID: KVM: arm64: Optimise module_change_host_page_prot

Merge the relaxation and restriction paths to both only need to adjust
permissions. This avoids un-map + re-map on the restriction path; and
avoids installing an annotated entry on the relaxation path (which
will cause a translation fault on first access by the host).

Bug: 308373293
Change-Id: I9c7a6ac149aad64b19a5ce7808334188475b27cc
Signed-off-by: Keir Fraser <keirf@google.com>