[ARM] tegra: stingray: Use WL_REG_ON GPIO for BT

[ARM] tegra: stingray: Use WL_REG_ON GPIO for BT

BT was using BT_REG_ON and Wlan was using WL_REG_ON.
4329 ORs both these GPIOs. However, there are problems
with BT_REG_ON while coming out of LP0 suspend.
So temporaraily have both wifi and BT use the same GPIO
for power on. For BT, set the BT_REG_ON to output low.

Change-Id: I75606ba124418fc7c606b434e4b7968fbc046228
Signed-off-by: Jaikumar Ganesh <jaikumar@google.com>