MFC r256328:
 Document XENHVM and xenpci are mutually inclusive.

Approved by:    re (delphij)
Sponsored by:   The FreeBSD Foundation
MFH (r256332): remove extraneous \n

Approved by:	re (gjb)
MFH (r256334): remove extraneous but harmless /

Approved by:	re (gjb)