ASoC: core: Return -ENOTSUPP from set_sysclk() if no operation provided

Make it easier for generic code to work with set_sysclk() by distinguishing
between the operation not being supported and an error as is done for
other operations like set_dai_fmt()

Signed-off-by: Mark Brown <broonie@linaro.org>
diff --git a/sound/soc/soc-core.c b/sound/soc/soc-core.c
index 03c779e..0ebf1da 100644
--- a/sound/soc/soc-core.c
+++ b/sound/soc/soc-core.c
@@ -3484,7 +3484,7 @@
 		return dai->codec->driver->set_sysclk(dai->codec, clk_id, 0,
 						      freq, dir);
 	else
-		return -EINVAL;
+		return -ENOTSUPP;
 }
 EXPORT_SYMBOL_GPL(snd_soc_dai_set_sysclk);
 
@@ -3505,7 +3505,7 @@
 		return codec->driver->set_sysclk(codec, clk_id, source,
 						 freq, dir);
 	else
-		return -EINVAL;
+		return -ENOTSUPP;
 }
 EXPORT_SYMBOL_GPL(snd_soc_codec_set_sysclk);