ASoC: wcd9xxx: integrate 4-pole extension cable support

Commit 07b6bd6a9a1e431a86efa76b14030d882ee7771b is checked into wcd9310
driver to support 4-pole extension cable detection.
Integrate the commit to wcd9xxx-mbhc driver.

Change-Id: I44973b5d9562b71b041498e3c9ad9709f4266181
Signed-off-by: Joonwoo Park <joonwoop@codeaurora.org>
diff --git a/sound/soc/codecs/wcd9xxx-mbhc.h b/sound/soc/codecs/wcd9xxx-mbhc.h
index 0934b5e..fb1dfdc 100644
--- a/sound/soc/codecs/wcd9xxx-mbhc.h
+++ b/sound/soc/codecs/wcd9xxx-mbhc.h
@@ -185,6 +185,7 @@
 	unsigned int gpio_irq;
 	int gpio_level_insert;
 	bool insert_detect; /* codec has own MBHC_INSERT_DETECT */
+	bool detect_extn_cable;
 	/* swap_gnd_mic returns true if extern GND/MIC swap switch toggled */
 	bool (*swap_gnd_mic) (struct snd_soc_codec *);
 };