ASoC: atmel-i2s: do not warn if muxclk is missing

Besides the fact that muxclk is optional, muxclk can be set using
assigned-clocks, removing the need to set it in driver. The warning is
thus unneeded, so we can transform it in a debug print, eventually to just
reflect that muxclk was not set by the driver.
Signed-off-by: Codrin Ciubotariu <codrin.ciubotariu@microchip.com>
Link: https://lore.kernel.org/r/20201103100554.1307190-1-codrin.ciubotariu@microchip.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/atmel/atmel-i2s.c

@@ -563,7 +563,7 @@ static int atmel_i2s_sama5d2_mck_init(struct atmel_i2s_dev *dev,
 		err = PTR_ERR(muxclk);
 		if (err == -EPROBE_DEFER)
 			return -EPROBE_DEFER;
-		dev_warn(dev->dev,
+		dev_dbg(dev->dev,
 			"failed to get the I2S clock control: %d\n", err);
 		return 0;
 	}