[media] cx23885: Don't leak firmware in cx23885_card_setup()

We leak the memory allocated to 'fw' (the firmware) when the variable goes
out of scope.
Fix the leak by calling release_firmware(fw) before 'fw' goes out of
scope.

Signed-off-by: Jesper Juhl <jj@chaosbits.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>