chromeos: Add PRESUBMIT.cfg

This adds back the presubmit hook configuration file
for the ChromeOS build system / repo utility.

BUG=chrome-os-partner:18638
TEST=upload a change to gerrit without --no-verify
     and see that repo does not complain about the license
     headers anymore.

Change-Id: I82a31afaf2b01a77a2d09da49f5c7a6531dc7681
Signed-off-by: Stefan Reinauer <reinauer@google.com>
Reviewed-on: https://gerrit.chromium.org/gerrit/49772
Reviewed-by: Duncan Laurie <dlaurie@chromium.org>

PRESUBMIT.cfg

@@ -0,0 +1,9 @@
+# This config file disables some of the ChromiumOS source style checks for
+# coreboot as they are directly conflicting with the coreboot coding
+# guidelines.
+
+[Hook Overrides]
+#stray_whitespace_check: false
+#long_line_check: false
+cros_license_check: false
+tab_check: false