ARM: dts: omap4-droid4: Add bluetooth

Droid 4 has WL 1285C connected to the OMAP's UART4 port, which is
used for Bluetooth and most likely can also be used for controlling
the FM radio and GPS receivers.

Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>