[media] m5602_ov7660: return error at ov7660_init()

[media] m5602_ov7660: return error at ov7660_init()

It used to be a code that returns arror at ov7660_init.
However, this was removed by changeset 80ea433d:

@@ -231,33 +116,40 @@ int ov7660_init(struct sd *sd)
        if (dump_sensor)
                ov7660_dump_registers(sd);

-   err = ov7660_set_gain(&sd->gspca_dev, sensor_settings[GAIN_IDX]);
-   if (err < 0)
-           return err;
+ return 0;
+}

-   err = ov7660_set_auto_white_balance(&sd->gspca_dev,
-           sensor_settings[AUTO_WHITE_BALANCE_IDX]);
-   if (err < 0)
-           return err;

As complained by gcc:
	drivers/media/usb/gspca/m5602/m5602_ov7660.c: In function 'ov7660_init':
	drivers/media/usb/gspca/m5602/m5602_ov7660.c:99:9: warning: variable 'err' set but not used [-Wunused-but-set-variable]

It should be noticed that the original error code was crappy, as it wasn't
returning any error if sensor init fails.

Fix it by returning an error if the sensor can't be initialized.

Cc: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>