[media] ddbridge: remove unneeded an NULL check

Static checkers complain about the inconsistent NULL check here.

There is an unchecked dereference of "input->fe" in the call to
tuner_attach_tda18271() and there is a second unchecked dereference a
couple lines later when we do:
	input->fe2->tuner_priv = input->fe->tuner_priv;

But actually "intput->fe" can't be NULL because if demod_attach_drxk()
fails to allocate it, then we would have return an error code.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>