x86: coreboot: Control I/O port 0xb2 writing via device tree

Writing 0xcb to I/O port 0xb2 (Advanced Power Management Control) causes
U-Boot to hang on QEMU q35 target. We introduce a config option in the
device tree "u-boot,no-apm-finalize" under /config node if we don't want
to do that.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Acked-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/x86/dts/qemu-x86_q35.dts b/arch/x86/dts/qemu-x86_q35.dts
index 6c89283..02a483c 100644
--- a/arch/x86/dts/qemu-x86_q35.dts
+++ b/arch/x86/dts/qemu-x86_q35.dts
@@ -15,6 +15,7 @@
 
 	config {
 		silent_console = <0>;
+		u-boot,no-apm-finalize;
 	};
 
 	chosen {