This enables Bluetooth modules in davinic_all_defconfig needed for LEGO
MINDSTORMS EV3.

Build CONFIG_SERIAL_DEV_BUS into the kernel since SERIAL_DEV_CTRL_TTYPORT
requires it so.
Signed-off-by: David Lechner <david@lechnology.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>