bttv: remove unused tea5757_set_freq declaration

tea5757_set_freq has been removed since
commit 1b500373 ("[media] bttv: Convert to generic
TEA575x interface").

So tea5757_set_freq is a unused declaration, remove it.
Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

drivers/media/pci/bt8xx/bttv.h

@@ -289,7 +289,6 @@ extern void bttv_init_card2(struct bttv *btv);
 extern void bttv_init_tuner(struct bttv *btv);
 
 /* card-specific functions */
-extern void tea5757_set_freq(struct bttv *btv, unsigned short freq);
 extern u32 bttv_tda9880_setnorm(struct bttv *btv, u32 gpiobits);
 
 /* extra tweaks for some chipsets */