MAINTAINERS: update SIANO drivers

Commit 786baecf ("[media] dvb-usb: move it to
drivers/media/usb/dvb-usb") moved the files, update the pattern.

Signed-off-by: Joe Perches <joe@perches.com>
Cc: Mauro Carvalho Chehab <mchehab@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>