ANDROID: KVM: arm64: Re-enable THP support for np-guests

There was a temporary tweak to user_mem_abort() to force all stage-2
mappings to page granularity as the upstream NP guest code didn't
support THP yet. Fix this situation, and remove the tweak from
user_mem_abort().

Bug: 357781595
Bug: 235345873
Change-Id: I64ed361ad9b6b8b8d4d23a1a5bac490559292ccb
Signed-off-by: Quentin Perret <qperret@google.com>