mb/google/hatch: Add support for variant_devtree_update()

This change adds support for variant_devtree_update()
that allows variant to update device tree.

BUG=None
TEST=emerge-hatch coreboot chromeos-bootimage

Change-Id: I0e9ad360b6c02c83fe49387ce7bc66d56448ffb9
Signed-off-by: David Wu <david_wu@quanta.corp-partner.google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/34399
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>

src/mainboard/google/hatch/ramstage.c

@@ -28,6 +28,7 @@ void mainboard_silicon_init_params(FSP_S_CONFIG *params)
 	size_t base_gpios;
 	size_t override_gpios;
 
+	variant_devtree_update();
 	base_table = base_gpio_table(&base_gpios);
 	override_table = override_gpio_table(&override_gpios);
 
@@ -37,6 +38,11 @@ void mainboard_silicon_init_params(FSP_S_CONFIG *params)
 					override_gpios);
 }
 
+void __weak variant_devtree_update(void)
+{
+	/* Override dev tree settings per board */
+}
+
 static void mainboard_enable(struct device *dev)
 {
 	mainboard_ec_init();

src/mainboard/google/hatch/variants/baseboard/include/baseboard/variants.h

@@ -43,4 +43,7 @@ const struct pad_config *variant_sleep_gpio_table(u8 slp_typ, size_t *num);
 /* Return ChromeOS gpio table and fill in number of entries. */
 const struct cros_gpio *variant_cros_gpios(size_t *num);
 
+/* Modify devictree settings during ramstage. */
+void variant_devtree_update(void);
+
 #endif /* BASEBOARD_VARIANTS_H */