x86: Add ifdtool for working with Intel Flash Descriptor ROM images

Newer Intel chips require a Management Engine which requires a particular
format for the SPI flash that contains the boot loader. Add a tool that
supports creating and modifying these ROM images.

This tool is from Chrome OS but has been cleaned up to use U-Boot style
and to add comments. A few features have been added also.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/Makefile b/tools/Makefile
index c422b76..a4216a1 100644
--- a/tools/Makefile
+++ b/tools/Makefile
@@ -126,6 +126,8 @@
 hostprogs-$(CONFIG_EXYNOS5420) += mkexynosspl
 HOSTCFLAGS_mkexynosspl.o := -pedantic
 
+hostprogs-$(CONFIG_X86) += ifdtool
+
 hostprogs-$(CONFIG_MX23) += mxsboot
 hostprogs-$(CONFIG_MX28) += mxsboot
 HOSTCFLAGS_mxsboot.o := -pedantic