[media] dib9000: get rid of warning: no previous prototype

drivers/media/dvb-frontends/dib9000.h:100:5: warning: no previous prototype for 'dib9000_remove_slave_frontend' [-Wmissing-prototypes]
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/dvb-frontends/dib9000.h

@@ -97,7 +97,7 @@ static inline int dib9000_set_slave_frontend(struct dvb_frontend *fe, struct dvb
 	return -ENODEV;
 }
 
-int dib9000_remove_slave_frontend(struct dvb_frontend *fe)
+static inline int dib9000_remove_slave_frontend(struct dvb_frontend *fe)
 {
 	printk(KERN_WARNING "%s: driver disabled by Kconfig\n", __func__);
 	return -ENODEV;