TBS A711 tablet has a bcm20702a1 bluetooth chip (part of AP6210 WiFi/BT
module) connected to UART1. Add node for the blutooth chip.

The driver needs brcm/BCM20702A1.hcd firmware file to run.
Signed-off-by: Ondrej Jirman <megous@megous.com>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>