x86: doc: Add porting hints for ACPI with Windows

Windows might cache system information and only detect ACPI changes
if you modify the ACPI table versions.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/doc/README.x86 b/doc/README.x86
index 75762de..4d50feb 100644
--- a/doc/README.x86
+++ b/doc/README.x86
@@ -982,6 +982,12 @@
 to U-Boot. This should go at the top of each file and list the coreboot
 filename where the code originated.
 
+Debugging ACPI issues with Windows:
+
+Windows might cache system information and only detect ACPI changes if you
+modify the ACPI table versions. So tweak them liberally when debugging ACPI
+issues with Windows.
+
 ACPI Support Status
 -------------------
 Advanced Configuration and Power Interface (ACPI) [16] aims to establish