ARM: dts: imx6qdl-gw5910: add support for bcm4330-bt

The Sterling-LWB has a BCM4330 which has a UART based bluetooth
HCI. Add support for binding to the bcm_hci driver to take care
of handling the shutdown gpio and loading firmware.

Because the shutdown gpio is more of an enable than a regulator
go ahead and replace the regulator with a shutdown-gpio.

Signed-off-by: Tim Harvey <tharvey@gateworks.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>