[media] radio-aimslab.c: get rid of warning: no previous prototype

drivers/media/radio/radio-aimslab.c:85:6: warning: no previous prototype for 'rtrack_set_pins' [-Wmissing-prototypes]

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/drivers/media/radio/radio-aimslab.c b/drivers/media/radio/radio-aimslab.c
index 12c70e8..a739ad4 100644
--- a/drivers/media/radio/radio-aimslab.c
+++ b/drivers/media/radio/radio-aimslab.c
@@ -82,7 +82,7 @@
 #define AIMS_BIT_VOL_UP		(1 << 6)	/* active low */
 #define AIMS_BIT_VOL_DN		(1 << 7)	/* active low */
 
-void rtrack_set_pins(void *handle, u8 pins)
+static void rtrack_set_pins(void *handle, u8 pins)
 {
 	struct radio_isa_card *isa = handle;
 	struct rtrack *rt = container_of(isa, struct rtrack, isa);