iio: frequency: adf4350: using an uninitialized variable

GCC complains that we use an uninitialized variable if the user passes
an invalid parameter to adf4350_read(). I decided that we should return
-EINVAL instead in that case.

However, when I looked up at adf4350_write() it returned -ENODEV for
that condition. In the end, I decided the -EINVAL was the right thing
and I change adf4350_write() to match.

Signed-off-by: Dan Carpenter <[e-mail]>
Acked-by: Michael Hennerich <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/iio/frequency/adf4350.c

···
 		adf4350_sync_config(st);
 		break;
 	default:
-		ret = -ENODEV;
+		ret = -EINVAL;
 	}
 	mutex_unlock(&indio_dev->mlock);
 
···
 		val = !!(st->regs[ADF4350_REG2] & ADF4350_REG2_POWER_DOWN_EN);
 		break;
 	default:
-		ret = -ENODEV;
+		ret = -EINVAL;
 	}
 	mutex_unlock(&indio_dev->mlock);