GENERIC Kernel Build errors with -fsanitize=undefined option enabled

[Harry Pantazis <luserx0%gmail.com@localhost>]

Greetings,

I'm working on the task of utilizing Undefined Behavior checks for the
NetBSD/amd64 kernel (KUBSan). I have built the GENERIC kernel with the
-fsanitize=undefined option enabled and I've caught a first series of
errors caused indirectly by Undefined Behavior.

This first errors are located in
src/sys/external/bsd/drm2/dist/drm/i915/intel_ddi.c and are specific
to the switch statement concerning that the case FLA