dm: pch: Add get_gpio_base op

x86 GPIO registers are accessed via I/O port whose base address is
configured in a PCI configuration register on the PCH device. Add
an op get_gpio_base to get the GPIO base address from PCH.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/pch/pch-uclass.c b/drivers/pch/pch-uclass.c
index b33d502..48a3965 100644
--- a/drivers/pch/pch-uclass.c
+++ b/drivers/pch/pch-uclass.c
@@ -33,6 +33,17 @@
 	return ops->set_spi_protect(dev, protect);
 }
 
+int pch_get_gpio_base(struct udevice *dev, u32 *gbasep)
+{
+	struct pch_ops *ops = pch_get_ops(dev);
+
+	*gbasep = 0;
+	if (!ops->get_gpio_base)
+		return -ENOSYS;
+
+	return ops->get_gpio_base(dev, gbasep);
+}
+
 static int pch_uclass_post_bind(struct udevice *bus)
 {
 	/*