msm: 9615: WLAN PMIC GPIO 6 configuration.

PMIC GPIO 6 maps to WLAN_CLK_PWR_REQ on AR6003. This GPIO needs to be
high for using 19.2MHz TCXO from PMIC.
Adding PMIC GPIO 6 entry in board specific file and keeping it low so
that AR6003 driver can set it to high if required.

Change-Id: Ie3cea7c0abc5ed5f5e09efc1455aa0f17138ac8b
CRs-Fixed: 373396
Signed-off-by: Pavan Kumar <pavan@codeaurora.org>