arm: dts: mt7988-sd-rfb: add SD pin driving settings

Set SD pin driving to 4mA

diff --git a/arch/arm/dts/mt7988.dtsi b/arch/arm/dts/mt7988.dtsi
index ac476d5..5c0c5bc 100644
--- a/arch/arm/dts/mt7988.dtsi
+++ b/arch/arm/dts/mt7988.dtsi
@@ -9,6 +9,7 @@
 #include <dt-bindings/clock/mt7988-clk.h>
 #include <dt-bindings/reset/mt7988-reset.h>
 #include <dt-bindings/gpio/gpio.h>
+#include <dt-bindings/pinctrl/mt65xx.h>
 #include <dt-bindings/phy/phy.h>
 
 / {