[media] rtl28xxu: properly initialize pdata

As complained by smatch:
	drivers/media/usb/dvb-usb-v2/rtl28xxu.c:1159 rtl2832u_tuner_attach() info: 'pdata' is not actually initialized (unreached code).

Cc: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>