ASoC: msm: 8084: remove unused code for MCLK GPIO

Codec MCLK for APQ8084 devices are supplied from PMIC using
PMIC GPIO 15. This GPIO is controlled from PMIC code itself. Remove
the unused code to set PMIC GPIO 15 for codec MCLK.

Change-Id: I04db0d9ad4962169835649cb1ea42796128aeecb
Signed-off-by: Banajit Goswami <bgoswami@codeaurora.org>