ARM: dts: sunxi: bananapi-m2-plus: Increase BT UART speed

Bluetooth module on BananaPi M2 Plus can also be used for streaming
audio. However, for that case higher UART speed is required.

Add a max-speed property.

Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
Acked-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/20210116105228.847073-1-jernej.skrabec@siol.net

arch/arm/boot/dts/sunxi-bananapi-m2-plus.dtsi

@@ -219,6 +219,7 @@
 
 	bluetooth {
 		compatible = "brcm,bcm43438-bt";
+		max-speed = <1500000>;
 		clocks = <&rtc 1>;
 		clock-names = "lpo";
 		vbat-supply = <&reg_vcc3v3>;