Remove a stale comment.

Approved by:	re (gjb)
Add manpages for VOP_ADVISE() and VOP_ALLOCATE().

Approved by:	re (gjb)
Make isci(4) loadable.

Reviewed by:	jimharris
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Approved by:	re (gjb)