[media] cx23885-dvb: initialize a8293_pdata

As reported by smatch:
	drivers/media/pci/cx23885/cx23885-dvb.c:2174 dvb_register() info: 'a8293_pdata' is not actually initialized (unreached code).

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