msync(2) must return ENOMEM and not EINVAL when the address is outside the
allowed range or when one or more pages are not mapped. This according to
The Open Group Base Specifications Issue 7.

Discussed with:	 attilio, Bruce Evans
Reviewed by:	 alc, Garrett Cooper
Reported by:	 ATF
MFC after:	 2 weeks
Sponsored by:	EMC / Isilon storage division