iio: mma9551: fix sparse warning

sparse warnings: (new ones prefixed by >>)

>> drivers/iio/accel/mma9551.c:554:57: sparse: mixing different enum types
drivers/iio/accel/mma9551.c:554:57: int enum mma9551_tilt_axis versus
drivers/iio/accel/mma9551.c:554:57: int enum mma9551_gpio_pin
>> drivers/iio/accel/mma9551.c:576:57: sparse: mixing different enum types
drivers/iio/accel/mma9551.c:576:57: int enum mma9551_tilt_axis versus
drivers/iio/accel/mma9551.c:576:57: int enum mma9551_gpio_pin

Signed-off-by: Vlad Dogaru <[e-mail]>
Reported-by: kbuild test robot <[e-mail]>
Reviewed-by: Irina Tirdea <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>

drivers/iio/accel/mma9551.c

···
 		return 0;
 
 	if (state == 0) {
-		ret = mma9551_gpio_config(data->client, mma_axis,
+		ret = mma9551_gpio_config(data->client,
+					  (enum mma9551_gpio_pin)mma_axis,
 					  MMA9551_APPID_NONE, 0, 0);
 		if (ret < 0)
 			return ret;
···
 			return -EINVAL;
 		}
 
-		ret = mma9551_gpio_config(data->client, mma_axis,
+		ret = mma9551_gpio_config(data->client,
+					  (enum mma9551_gpio_pin)mma_axis,
 					  MMA9551_APPID_TILT, bitnum, 0);
 		if (ret < 0)
 			return ret;