add a knob for kernel splitconfig checks

This allows kernel repos to opt-in/out to the splitconfig checks.

BUG=chromium:466264
TEST=CQ passes

Change-Id: I713cbc69f2e0994dd9643459133a963dc7f13131
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/repohooks/+/2595356
Reviewed-by: Guenter Roeck <groeck@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
diff --git a/pre-upload.py b/pre-upload.py
index 5e52681..2407ac5 100755
--- a/pre-upload.py
+++ b/pre-upload.py
@@ -2177,6 +2177,7 @@
     'filepath_chartype_check': _check_filepath_chartype,
     'cargo_clippy_check': _check_cargo_clippy,
     'exec_files_check': _check_exec_files,
+    'kernel_splitconfig_check': _kernel_configcheck,
 }