Bluetooth: Add Sleep Support using GPIO for ATH3K driver.

Two additional GPIO pins are used to support sleep mechanism
between Host and Atheros BT SoC.

Change-Id: If7d49e23d285b8e416af729314cffdf7c62da136
Signed-off-by: Santosh Sajjan <ssajjan@codeaurora.org>
Signed-off-by: Ram Mohan Korukonda <rkorukon@codeaurora.org>