Kconfig: Create a new tools menu

At present MKIMAGE_DTC_PATH is in the devicetree menu but not within
'devicetree control' since it does not relate to that. As a result it
shows up in the top menu.

It actually relates to the mkimage tool, so create a new tools menu for it
and move it there.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/Kconfig b/tools/Kconfig
new file mode 100644
index 0000000..b2f5012
--- /dev/null
+++ b/tools/Kconfig
@@ -0,0 +1,12 @@
+menu "Tools options"
+
+config MKIMAGE_DTC_PATH
+	string "Path to dtc binary for use within mkimage"
+	default "dtc"
+	help
+	  The mkimage host tool will, in order to generate FIT images make
+	  calls to the dtc application in order to create the output.  In
+	  some cases the system dtc may not support all required features
+	  and the path to a different version should be given here.
+
+endmenu