bluetooth: Add low-power mode to support Bluedroid

 * Add procfs interface to control LPM
 * Add wake_peer hooks to wake up the msm_serial_hs device
 * Specific to Broadcom hardware

Change-Id: Ic3068a9502c65274f31b44ca918b8901c20b891a
bluetooth: Fix race conditions in BT LPM

 * Use workqueues and fix bugs in bluesleep (similar to JF).

Change-Id: I858bc6a9db09371b40bc1d0d981df3aacb362560
drivers: bluesleep_bcm: Fix unused-variable warnings