[media] cx18: fix sparse warnings

/home/hans/work/build/media-git/drivers/media/pci/cx18/cx18-firmware.c:169:32: warning: cast to restricted __le32
/home/hans/work/build/media-git/drivers/media/pci/cx18/cx18-firmware.c:170:32: warning: cast to restricted __le32
/home/hans/work/build/media-git/drivers/media/pci/cx18/cx18-firmware.c:171:31: warning: cast to restricted __le32
/home/hans/work/build/media-git/drivers/media/pci/cx18/cx18-firmware.c:172:31: warning: cast to restricted __le32

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