x86: minnowmax: add GPIO banks in the device tree

There are 6 banks:
    4 banks for CORE: available in S0 mode
    2 banks for SUS (Suspend): available in S0-S5 mode

Signed-off-by: Gabriel Huau <contact@huau-gabriel.fr>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Acked-by: Simon Glass <sjg@chromium.org>

arch/x86/dts/minnowmax.dts

@@ -22,6 +22,48 @@
 		silent_console = <0>;
 	};
 
+	gpioa {
+		compatible = "intel,ich6-gpio";
+		u-boot,dm-pre-reloc;
+		reg = <0 0x20>;
+		bank-name = "A";
+	};
+
+	gpiob {
+		compatible = "intel,ich6-gpio";
+		u-boot,dm-pre-reloc;
+		reg = <0x20 0x20>;
+		bank-name = "B";
+	};
+
+	gpioc {
+		compatible = "intel,ich6-gpio";
+		u-boot,dm-pre-reloc;
+		reg = <0x40 0x20>;
+		bank-name = "C";
+	};
+
+	gpiod {
+		compatible = "intel,ich6-gpio";
+		u-boot,dm-pre-reloc;
+		reg = <0x60 0x20>;
+		bank-name = "D";
+	};
+
+	gpioe {
+		compatible = "intel,ich6-gpio";
+		u-boot,dm-pre-reloc;
+		reg = <0x80 0x20>;
+		bank-name = "E";
+	};
+
+	gpiof {
+		compatible = "intel,ich6-gpio";
+		u-boot,dm-pre-reloc;
+		reg = <0xA0 0x20>;
+		bank-name = "F";
+	};
+
 	chosen {
 		stdout-path = "/serial";
 	};