x86: coreboot: Add the missing pc speaker node in the device tree

This is currently missing and without it the i8254 beeper driver
won't work.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/x86/dts/coreboot.dts b/arch/x86/dts/coreboot.dts
index e212f3d..a88da6e 100644
--- a/arch/x86/dts/coreboot.dts
+++ b/arch/x86/dts/coreboot.dts
@@ -10,6 +10,7 @@
 /include/ "skeleton.dtsi"
 /include/ "serial.dtsi"
 /include/ "keyboard.dtsi"
+/include/ "pcspkr.dtsi"
 /include/ "reset.dtsi"
 /include/ "rtc.dtsi"
 /include/ "tsc_timer.dtsi"