Account for the mapped pages in the kernel_pmap on x86 in
pmap_mapdev(). The pmap_unmapdev() on stable/9 calls pmap_remove() to
clear the range, which decrements kernel_pmap.pm_stats.resident_count.
Misaccounting causes miscellaneous failures, since pmap_remove() tests
the counter for zero and does nothing.

This is direct commit to stable/9, since HEAD and stable/10 use vmem
and do not utilize pmap_remove() etc.

Based on the submission by: Kohji Okuno <okuno.kohji at jp.panasonic.com>