arm64: dts: rockchip: Fix Bluetooth stability on LCKFB TaiShan Pi

arm64: dts: rockchip: Fix Bluetooth stability on LCKFB TaiShan Pi

The AP6212 WiFi/BT module on the LCKFB TaiShan Pi (RK3566) is prone to
communication timeouts and reset failures (error -110) when operating at
3 Mbps.

This patch stabilizes the Bluetooth interface by:
1. Updating the compatible string to 'brcm,bcm43430a1-bt' to better reflect
   the actual chip revision used in the AP6212 module.
2. Lowering the maximum UART baud rate from 3,000,000 to 1,500,000 bps.
   Tests show that 1.5 Mbps is the reliable upper limit for this board's
   UART configuration, eliminating the initialization timeouts.

Fixes: 251e5ade9ba4 ("arm64: dts: rockchip: add dts for LCKFB Taishan Pi RK3566")
Signed-off-by: Ming Wang <wangming5719@gmail.com>
Link: https://patch.msgid.link/20260206090453.1041919-1-wming126@126.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>