[media] radio-isa: get rid of warning: no previous prototype

drivers/media/radio/radio-isa.c:194:24: warning: no previous prototype for 'radio_isa_alloc' [-Wmissing-prototypes]
drivers/media/radio/radio-isa.c:210:5: warning: no previous prototype for 'radio_isa_common_probe' [-Wmissing-prototypes]
drivers/media/radio/radio-isa.c:290:5: warning: no previous prototype for 'radio_isa_common_remove' [-Wmissing-prototypes]

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/radio/radio-isa.c

@@ -191,7 +191,7 @@ static bool radio_isa_valid_io(const struct radio_isa_driver *drv, int io)
 	return false;
 }
 
-struct radio_isa_card *radio_isa_alloc(struct radio_isa_driver *drv,
+static struct radio_isa_card *radio_isa_alloc(struct radio_isa_driver *drv,
 				struct device *pdev)
 {
 	struct v4l2_device *v4l2_dev;
@@ -207,8 +207,9 @@ struct radio_isa_card *radio_isa_alloc(struct radio_isa_driver *drv,
 	return isa;
 }
 
-int radio_isa_common_probe(struct radio_isa_card *isa, struct device *pdev,
-				int radio_nr, unsigned region_size)
+static int radio_isa_common_probe(struct radio_isa_card *isa,
+				  struct device *pdev,
+				  int radio_nr, unsigned region_size)
 {
 	const struct radio_isa_driver *drv = isa->drv;
 	const struct radio_isa_ops *ops = drv->ops;
@@ -287,7 +288,8 @@ err_dev_reg:
 	return res;
 }
 
-int radio_isa_common_remove(struct radio_isa_card *isa, unsigned region_size)
+static int radio_isa_common_remove(struct radio_isa_card *isa,
+				   unsigned region_size)
 {
 	const struct radio_isa_ops *ops = isa->drv->ops;