(cherry picked from commit 1a3932e0)

V4L: cx18: Upgrade to newer firmware & update cx18 documentation

Conexant graciously gave us permission to redistribute the
firmware. Update the documentation where the firmware can be
downloaded.
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>
Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>