[media] af9015: fix sparse warning

drivers/media/usb/dvb-usb-v2/af9015.c:422:38: warning: cast to restricted __le32

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