arm64: dts: allwinner: a64: bananapi-m64: Add Bluetooth device node

arm64: dts: allwinner: a64: bananapi-m64: Add Bluetooth device node

The AP6212 is based on the Broadcom BCM43430 or BCM43438. The WiFi side
identifies as BCM43430, while the Bluetooth side identifies as BCM43438.

The Bluetooth side is connected to UART1 in a 4 wire configuration. Same
as the WiFi side, due to being the same chip and package, DLDO2 provides
overall power via VBAT, and DLDO4 provides I/O power via VDDIO. The RTC
clock output provides the LPO low power clock at 32.768 kHz.

This patch enables Bluetooth on this board, and also adds the missing
LPO clock on the WiFi side. There is also a PCM connection for Bluetooth,
but this is not covered here.

Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Chen-Yu Tsai <wens@csie.org>