x86: link: Add PCH driver to support SPI Flash

U-Boot on coreboot does not have a driver for the PCH so cannot see the
SPI peripheral now that it has moved inside the PCH. Add a simple driver so
that SPI flash works again.

Signed-off-by: Simon Glass <sjg@chromium.org>

arch/x86/cpu/coreboot/pci.c

@@ -34,3 +34,14 @@ U_BOOT_DRIVER(pci_x86_drv) = {
 	.of_match	= pci_x86_ids,
 	.ops		= &pci_x86_ops,
 };
+
+static const struct udevice_id generic_pch_ids[] = {
+	{ .compatible = "intel,pch" },
+	{ }
+};
+
+U_BOOT_DRIVER(generic_pch_drv) = {
+	.name		= "pch",
+	.id		= UCLASS_PCH,
+	.of_match	= generic_pch_ids,
+};

arch/x86/dts/chromebook_link.dts

@@ -181,7 +181,7 @@
 
 		pch {
 			reg = <0x0000f800 0 0 0 0>;
-			compatible = "intel,bd82x6x";
+			compatible = "intel,bd82x6x", "intel,pch";
 			u-boot,dm-pre-reloc;
 			#address-cells = <1>;
 			#size-cells = <1>;