objtool, kcsan: Add __tsan_read_write to uaccess whitelist

Adds the new __tsan_read_write compound instrumentation to objtool's
uaccess whitelist.

Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>