[media] cx231xx: fix undefined function cx231xx_g_chip_ident()

This patch:
http://git.linuxtv.org/media_tree.git/commit/b86d15440b683f8634c0cb26fc0861a5bc4913ac
is missing a chunk when compared to an older version:
https://patchwork.kernel.org/patch/2063281/
probably because of an unresolved merging conflict.
This causes the following error:
WARNING: "cx231xx_g_chip_ident" [/home/jena/media_build/v4l/cx231xx.ko] undefined!

Signed-off-by: Gianluca Gennari <gennarone@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>