arm64: Use page_to_pvh() when the vm_page_t is known

arm64: Use page_to_pvh() when the vm_page_t is known

When support for a sparse pv_table was added, the implementation of
pa_to_pvh() changed from a simple constant-time calculation to iterating
over the array vm_phys_segs[].  To mitigate this issue, an alternative
function, page_to_pvh(), was introduced that still runs in constant time
but requires the vm_page_t to be known.  However, three cases where the
vm_page_t is known were not converted to page_to_pvh().  This change
converts those three cases.

Reviewed by:	kib, markj
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D30832