V4L/DVB: MAINTAINERS: tag pvrusb2 list as subscribers-only

V4L/DVB: MAINTAINERS: tag pvrusb2 list as subscribers-only

Posting to the pvrusb2 mailing list is for subscribers only.  Anyone can
subscribe of course.  This is done purely to keep spammers and similar pond
scum from bothering the subscribers of the list.  This patch marks the
pvrusb2 list tag in MAINTAINERS to reflect this situation.

Signed-off-by: Mike Isely <isely@pobox.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>