libbt: Add support for board-specific configuration

 * Set with BOARD_BLUEDROID_VENDOR_CONF

Change-Id: Ia657da71d0e3dad670def517fe3246556f8f6d5a

Conflicts:
	vnd_buildcfg.mk
libbt: BT USB support

1. Skip baud rate configuration
2. Read BD Address from device
3. No specific configuration is required for SCO
4. SCO does not use I2S interface

Issue: AXIA-1459
Issue: AXIA-1460
Change-Id: I22a8cdde2b5b2ad11b21e7d1d2578b4323e812b2
Signed-off-by: Ravindranath Doddi <ravindranathx.doddi@wipro.com>
libbt: Add btlock support

 * Concurrent WiFi/BT firmware loading can cause a chip crash.
 * Kernel supports a btlock device which is a simple semaphore that can
   protect from this situation.
 * Add support in the Bluedroid vendor lib for this on the BT side, as
   WiFi is already done directly in the kernel.

Change-Id: I8b9d3b1ccd06cc5d5528c7d6d685048c258d9887
libbt: Add prepatch support

 * We need to apply an initial patch to the BCM4335 hardware to prevent
   chip crashes, so add support for a prepatch designated by
   FW_PRE_PATCH.

Change-Id: I2d2ec59094a1ae2cb39e1f41d4853ac4a45d1902
libbt: Fix stray comma :)

Change-Id: I0440c359a4c3c919695e928491915c32d7cf695b
libbt: Add support for using two stop bits

 * This improves reliability on chips such as BCM4335.
 * Also externalize some configuration.

Change-Id: I1271f0c1c3e602c8bfe9f816f57c9cb6add04b3a