Documentation: Make sure ifdtool/index gets added to toctree

Change-Id: I57b37ebd3383e73a101511e303ad3beeb9d4ea31
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/36109
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Patrick Rudolph <siro@das-labor.org>

Documentation/ifdtool/index.md

@@ -1,3 +1,4 @@
+# ifdtool
 
 Contents:
 

Documentation/util.md

@@ -1,4 +1,7 @@
 # Utilities
+
+## List of utils
+
 _Scripts and programs found in the `./util` directory_
 * __abuild__ - coreboot autobuild script builds coreboot images for all
 available targets. `bash`
@@ -131,3 +134,8 @@ CPUs. `C`
 * __x86__ - Generates 32-bit PAE page tables based on a CSV input file.
 `Go`
 * __xcompile__ - Cross compile setup `Bash`
+
+
+## In depth documentation
+
+* [ifdtool](ifdtool/index.md)