ANDROID: KVM: arm64: Make __pkvm_host_dirty_log_guest() upstream-friendly

The __pkvm_host_*_guest() functions upstream all follow a consistent
coding pattern. Make __pkvm_host_dirty_log_guest() follow the same
thing. This allows to remove the host __check_host_unshare_guest()
function that has been superseded by __check_host_shared_guest()
upstream.

Note that we will eventually be able to simply remove
__pkvm_host_dirty_log_guest() altogether once we drop the GUP pin for
np-guest memory. This only helps get the code in a cleaner state on the
way there.

Bug: 357781595
Bug: 235345873
Change-Id: I89c6e1d29234075d5d859dd12b6228e0f820995c
Signed-off-by: Quentin Perret <qperret@google.com>