MFC r235375:

MFC r235375:
Add new pager type, OBJT_MGTDEVICE. It provides the device pager
which carries fictitous managed pges. In particular, the consumers of
the new object type can remove all mappings of the device page with
pmap_remove_all().

The range of physical addresses used for fake page allocation shall be
registered with vm_phys_fictitious_reg_range() interface to allow the
PHYS_TO_VM_PAGE() to work in pmap.

git-svn-id: svn://svn.freebsd.org/base/stable/9@236925 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f