Bluetooth: add Qualcomm In-Band Sleep support to hci_uart

Add new HCIUART protocol HCIUART_IBS which enables the Bluetooth
device to enter a low power state when possible.  It also tells
the msm_serial_hs UART driver that it may go to a low-power state
even though the port is open.

CRs-Fixed: 713897

Change-Id: I18207f076c9fb39c04275a8db2625a2d31bb0ae2
Signed-off-by: Mike Feldman <mfeldman@quicinc.com>
Git-commit: 81fda6eb1b506a36bcdbbe77a59b6fe82c997568
[ananthk@codeaurora.org: Resolved merge conflicts]
Signed-off-by: Anantha Krishnan <ananthk@codeaurora.org>