ARM64: dts: meson-gxbb: add the SDIO pins

This is used to configure the pins of the sd_emmc_a controller to
which an SDIO module is connected (when available).
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Tested-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>

arch/arm64/boot/dts/amlogic/meson-gxbb.dtsi

@@ -383,6 +383,25 @@ mux {
 					};
 				};
 
+				sdio_pins: sdio {
+					mux {
+						groups = "sdio_d0",
+						       "sdio_d1",
+						       "sdio_d2",
+						       "sdio_d3",
+						       "sdio_cmd",
+						       "sdio_clk";
+						function = "sdio";
+					};
+				};
+
+				sdio_irq_pins: sdio_irq {
+					mux {
+						groups = "sdio_irq";
+						function = "sdio";
+					};
+				};
+
 				uart_a_pins: uart_a {
 					mux {
 						groups = "uart_tx_a",