Provide the unique implementation for the VOP_GETPAGES() method used
by ffs and ext2fs.  Remove duplicated call to vm_page_zero_invalid(),
done by VOP and by vm_pager_getpages().  Use vm_pager_free_nonreq().

Reviewed by:	alc (previous version)
Sponsored by:	The FreeBSD Foundation
MFC after:	6 weeks (after r271596)


git-svn-id: svn+ssh://svn.freebsd.org/base/head@271619 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f