rcutorture: Add srcu_lockdep.sh

This commit adds an srcu_lockdep.sh script that checks whether lockdep
correctly classifies SRCU-based, SRCU/mutex-based, and SRCU/rwsem-based
deadlocks.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
[ boqun: Fix "RCUTORTURE" with "$RCUTORTURE" ]
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>