[media] lmedm04: get rid of warning: no previous prototype

drivers/media/usb/dvb-usb-v2/lmedm04.c:802:13: warning: no previous prototype for 'lme_firmware_switch' [-Wmissing-prototypes]
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/usb/dvb-usb-v2/lmedm04.c

@@ -799,7 +799,7 @@ static const char fw_c_rs2000[] = LME2510_C_RS2000;
 static const char fw_lg[] = LME2510_LG;
 static const char fw_s0194[] = LME2510_S0194;
 
-const char *lme_firmware_switch(struct dvb_usb_device *d, int cold)
+static const char *lme_firmware_switch(struct dvb_usb_device *d, int cold)
 {
 	struct lme2510_state *st = d->priv;
 	struct usb_device *udev = d->udev;