V4L: cx88: Avoid a NULL pointer dereference during mpeg_open()

V4L: cx88: Avoid a NULL pointer dereference during mpeg_open()

(cherry picked from commit 48200baeab95fd39a7f4c4f3536c7142a64ac335)

[PATCH] V4L: cx88: Avoid a NULL pointer dereference during mpeg_open()

Bug: With a hardware encoder board installed as cx88[1] and a
non-encoder boards installed as cx88[0], an OOPS is generated
during cx8802_get_device() called from mpeg_open().

Signed-off-by: Steven Toth <stoth@hauppauge.com>
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>