x86: coreboot: Convert to use DM coreboot video driver

This converts coreboot to use DM framebuffer driver.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/x86/dts/broadwell_som-6896.dts b/arch/x86/dts/broadwell_som-6896.dts
index 4bb0a34..3966199 100644
--- a/arch/x86/dts/broadwell_som-6896.dts
+++ b/arch/x86/dts/broadwell_som-6896.dts
@@ -4,6 +4,7 @@
 /include/ "serial.dtsi"
 /include/ "rtc.dtsi"
 /include/ "tsc_timer.dtsi"
+/include/ "coreboot_fb.dtsi"
 
 / {
 	model = "Advantech SOM-6896";