vm_fault: handle KERN_PROTECTION_FAILURE

pmap_enter(PMAP_ENTER_LARGEPAGE) may return KERN_PROTECTION_FAILURE due to
PKRU inconsistency. Handle it in the call place from vm_fault_populate(),
and in places which decode errors from vm_fault_populate()/
vm_fault_allocate().

Reviewed by: jah, markj
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D29442