media: i2c: ov7251: Make the enable GPIO optional.

Not all implementations wire up the enable GPIO and may just tie
it to a supply rail.
Make it optional.

Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>

drivers/media/i2c/ov7251.c

@@ -1697,7 +1697,8 @@ static int ov7251_probe(struct i2c_client *client)
 		return PTR_ERR(ov7251->analog_regulator);
 	}
 
-	ov7251->enable_gpio = devm_gpiod_get(dev, "enable", GPIOD_OUT_HIGH);
+	ov7251->enable_gpio = devm_gpiod_get_optional(dev, "enable",
+						      GPIOD_OUT_HIGH);
 	if (IS_ERR(ov7251->enable_gpio)) {
 		dev_err(dev, "cannot get enable gpio\n");
 		return PTR_ERR(ov7251->enable_gpio);