[media] cx231xx: fix sparse warnings

[media] cx231xx: fix sparse warnings

drivers/media/usb/cx231xx/cx231xx-avcore.c:2226:15: warning: cast to restricted __le32
drivers/media/usb/cx231xx/cx231xx-avcore.c:2447:15: warning: cast to restricted __le32
drivers/media/usb/cx231xx/cx231xx-avcore.c:2475:15: warning: cast to restricted __le32
drivers/media/usb/cx231xx/cx231xx-avcore.c:2500:15: warning: cast to restricted __le32
drivers/media/usb/cx231xx/cx231xx-avcore.c:2647:18: warning: incorrect type in assignment (different base types)
drivers/media/usb/cx231xx/cx231xx-avcore.c:2659:21: warning: cast to restricted __le32
drivers/media/usb/cx231xx/cx231xx-dvb.c:743:57: warning: Using plain integer as NULL pointer
drivers/media/usb/cx231xx/cx231xx-dvb.c:776:57: warning: Using plain integer as NULL pointer

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>