V4L/DVB (10904): remove dib0070_ctrl_agc_filter from dib0070.h

This function prototype is defined but the function itself does not exist.
Signed-off-by: NMichael Krufky <mkrufky@linuxtv.org>
Signed-off-by: NMauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/dvb/frontends/dib0070.h

@@ -58,6 +58,4 @@ static inline u16 dib0070_wbd_offset(struct dvb_frontend *fe)
 }
 #endif
 
-extern void dib0070_ctrl_agc_filter(struct dvb_frontend *, uint8_t open);
-
 #endif