This fixes the following sparse warning:

drivers/media/i2c/adv748x/adv748x-afe.c:294:34:    expected unsigned int [usertype] *signal
drivers/media/i2c/adv748x/adv748x-afe.c:294:34:    got int *<noident>
drivers/media/i2c/adv748x/adv748x-afe.c:294:34: warning: incorrect type in argument 2 (different signedness)
Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>