ARM: OMAP/ASoC: Zoom2: Let the codec to handle the hs_extmute GPIO

Remove the use of set_hs_extmute callback and let the codec driver to
handle the extmute GPIO.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>