storm: invert dev_mode control

To keep dev mode switch consistent with other GPIOs (asserted low) -
invert dev_mode control on storm.

BUG=none
TEST=with the updated file dut-control properly reports the dev switch state.

Change-Id: I3949cbac106cba07a4b005ed9b84df30b83e7586
Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/217140
Reviewed-by: Todd Broch <tbroch@chromium.org>
diff --git a/servo/data/servo_storm_overlay.xml b/servo/data/servo_storm_overlay.xml
index db09c6d..027c8e3 100644
--- a/servo/data/servo_storm_overlay.xml
+++ b/servo/data/servo_storm_overlay.xml
@@ -2,4 +2,9 @@
   <include>
     <name>servoflex_v2_r0_p50.xml</name>
   </include>
+  <control>
+    <name>dev_mode</name>
+    <doc>dev_mode GPIO is inverted on storm</doc>
+    <params map="onoff_i" clobber_ok=""></params>
+  </control>
 </root>