[media] cx24117: prevent mutex to be stuck on locked state if FE init fails

This patch will fix the situation where the mutex was left in a
locked state if for some reason the FE init failed.

Signed-off-by: Luis Alves <ljalvs@gmail.com>
Reviewed-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>