kmemcheck: rip it out for real

Commit 4675ff05 ("kmemcheck: rip it out") has removed the code but
for some reason SPDX header stayed in place.  This looks like a rebase
mistake in the mmotm tree or the merge mistake.  Let's drop those
leftovers as well.

Signed-off-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>