The Bluetooth chip is capable of operating at 4Mbps, but the
max-speed setting was on the UART node instead of the Bluetooth
node, so the chip didn't operate at the correct speed resulting
in choppy audio.  Fix this by setting the max-speed in the proper
node.

Fixes: a1d8a344 ("arm64: dts: renesas: Introduce r8a774a1-beacon-rzg2m-kit")
Signed-off-by: Adam Ford <aford173@gmail.com>
Link: https://lore.kernel.org/r/20201213183759.223246-3-aford173@gmail.comSigned-off-by: Geert Uytterhoeven <geert+renesas@glider.be>