arm64: dts: rockchip: add rfkill node for M.2 Key E Bluetooth on Rock 5B

By default the BT WAKE signal inside the M.2 key E connector on Radxa
Rock 5B is driven low, which results in the Bluetooth function being
disabled even if the inserted M.2 card supports it. Expose this signal
as an RFKILL device so that it can be enabled by the userspace.

Tested with an Intel AX210 card, which connects a Bluetooth device over
the USB 2.0 bus.

Signed-off-by: Alexey Charkov <alchark@gmail.com>
Link: https://lore.kernel.org/r/20240517122509.4626-1-alchark@gmail.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>

arch/arm64/boot/dts/rockchip/rk3588-rock-5b.dts

@@ -65,6 +65,13 @@
 		shutdown-gpios = <&gpio4 RK_PA2 GPIO_ACTIVE_HIGH>;
 	};
 
+	rfkill-bt {
+		compatible = "rfkill-gpio";
+		label = "rfkill-m2-bt";
+		radio-type = "bluetooth";
+		shutdown-gpios = <&gpio3 RK_PD5 GPIO_ACTIVE_HIGH>;
+	};
+
 	vcc3v3_pcie2x1l0: vcc3v3-pcie2x1l0-regulator {
 		compatible = "regulator-fixed";
 		enable-active-high;