dm: x86: dts: Add additional info to the serial port node

Add more information so that U-Boot can find the address of the serial port.
Also fix the reg-shift value.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/x86/dts/link.dts b/arch/x86/dts/link.dts
index 67ce52a..f2fcb39 100644
--- a/arch/x86/dts/link.dts
+++ b/arch/x86/dts/link.dts
@@ -12,7 +12,23 @@
 	       silent_console = <0>;
 	};
 
-	gpio: gpio {};
+	gpioa {
+		compatible = "intel,ich6-gpio";
+		reg = <0 0x10>;
+		bank-name = "A";
+	};
+
+	gpiob {
+		compatible = "intel,ich6-gpio";
+		reg = <0x30 0x10>;
+		bank-name = "B";
+	};
+
+	gpioc {
+		compatible = "intel,ich6-gpio";
+		reg = <0x40 0x10>;
+		bank-name = "C";
+	};
 
 	serial {
 		reg = <0x3f8 8>;