[media] wl128x: fix int type for streg_cbdata

The streg_cbdata can have a negative error value. So, it should be
an integer, and not u8, as reported by smatch:
	drivers/media/radio/wl128x/fmdrv_common.c:1517 fmc_prepare() warn: assigning (-115) to unsigned variable 'fmdev->streg_cbdata'
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/radio/wl128x/fmdrv.h

@@ -210,7 +210,7 @@ struct fmdev {
 	spinlock_t resp_skb_lock; /* To protect access to received SKB */
 
 	long flag;		/*  FM driver state machine info */
-	u8 streg_cbdata; /* status of ST registration */
+	int streg_cbdata; /* status of ST registration */
 
 	struct sk_buff_head rx_q;	/* RX queue */
 	struct tasklet_struct rx_task;	/* RX Tasklet */