objtool, kcsan: Add KCSAN runtime functions to whitelist

This patch adds KCSAN runtime functions to the objtool whitelist.

Signed-off-by: Marco Elver <elver@google.com>
Acked-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>