arm64: dts: allwinner: orange-pi-3: Enable UART1 / Bluetooth

The board contains AP6256 WiFi/BT module that has its bluetooth part
connected to SoC's UART1 port. Enable this port, and add node for the
bluetooth device.

Bluetooth part is named bcm4345c5.

You'll need a BCM4345C5.hcd firmware file that can be found in the
Xulongs's repository for H6:

https://github.com/orangepi-xunlong/OrangePiH6_external/tree/master/ap6256



The driver expects the firmware at the following path relative to the
firmware directory:

  brcm/BCM4345C5.hcd

Signed-off-by: Ondrej Jirman <megous@megous.com>
Signed-off-by: Maxime Ripard <mripard@kernel.org>