Add two self test cases for the following case:

	P0:			P1:			P2:

				<in irq handler>
	spin_lock_irq(&slock)	read_lock(&rwlock)
							write_lock_irq(&rwlock)
	read_lock(&rwlock)	spin_lock(&slock)

, which is a deadlock, as the read_lock() on P0 cannot get the lock
because of the fairness.

	P0:			P1:			P2:

	<in irq handler>
	spin_lock(&slock)	read_lock(&rwlock)
							write_lock(&rwlock)
	read_lock(&rwlock)	spin_lock_irq(&slock)

, which is not a deadlock, as the read_lock() on P0 can get the lock
because it could use the unfair fastpass.
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20200807074238.1632519-19-boqun.feng@gmail.com