ASoC: zoom2: Remove HS mux GPIO handling to avoid kernel crash due to BUG_ON()

The machine driver try to use GPIO15 of twl4030 for HS MUX which supposed to
select between TWL's HSOL/R and tlv320aic3254's HPL/R.
The TWL's GPIO allocated dynamically so the (OMAP_MAX_GPIO_LINES + 15) is no
longer valid GPIO number causing a kernel crash due to BUG_ON()
Also the current machine driver supports only TWL audio currently: there is
no need to control the GPIO.

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