Bluetooth: hci_bcm: Add BCM20702A1 variant

The BCM20702A1 chip is a single-chip Bluetooth 4.0 controller and
transceiver. It is found in the AMPAK AP6210 WiFi+BT package.

Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Tested-by: Ondrej Jirman <megous@megous.com>
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>