[media] ngene: preventing dereferencing a NULL pointer

As reported by smatch:
	drivers/media/pci/ngene/ngene-core.c:1529 init_channel() error: we previously assumed 'chan->fe' could be null (see line 1521)

Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>