V4L/DVB (5315): Tda1004x: check request firmware for NULL ponter again

In older versions, this was used to decide whether to boot from
eeprom or file. This is no longer necessary but the check helps to avoid
an oops with misconfigured cards.

Signed-off-by: Hartmut Hackmann <hartmut.hackmann@t-online.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>