In general, when we map a page into the kernel's address space, we no

In general, when we map a page into the kernel's address space, we no
longer create a pv entry for that mapping.  (The two exceptions are
mappings into the kernel's exec and pipe submaps.)  Consequently, there is
no reason for get_pv_entry() to dig deep into the free page queues, i.e.,
use VM_ALLOC_SYSTEM, by default.  This revision changes get_pv_entry() to
use VM_ALLOC_NORMAL by default, i.e., before calling pmap_collect() to
reclaim pv entries.

Approved by:	re (kensmith)