[media] af9013: Fix a compilation warning

drivers/media/dvb/frontends/af9013.c: In function ‘af9013_update_signal_strength.clone.0’:
drivers/media/dvb/frontends/af9013.c:967:6: warning: ‘ret’ may be used uninitialized in this function

Cc: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/dvb/frontends/af9013.c

@@ -964,7 +964,7 @@ error:
 static int af9013_update_signal_strength(struct dvb_frontend *fe)
 {
 	struct af9013_state *state = fe->demodulator_priv;
-	int ret;
+	int ret = 0;
 	u8 rf_gain, if_gain;
 	int signal_strength;