Relax one of the conditions for mapping a page on the fast path.

Reviewed by:	kib
X-MFC with:	r270011
Sponsored by:	EMC / Isilon Storage Division


git-svn-id: svn+ssh://svn.freebsd.org/base/head@270387 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f