ASoC: Rename WM8994 detecting flag to mic_detecting

More specific and avoids confusion with a following change.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
diff --git a/sound/soc/codecs/wm8994.h b/sound/soc/codecs/wm8994.h
index 77e3d8c..8622bc4 100644
--- a/sound/soc/codecs/wm8994.h
+++ b/sound/soc/codecs/wm8994.h
@@ -127,7 +127,7 @@
 	struct soc_enum enh_eq_enum;
 
 	struct wm8994_micdet micdet[2];
-	bool detecting;
+	bool mic_detecting;
 	bool jack_mic;
 	int btn_mask;