locking/rtmutex: Squash self-deadlock check for ww_rt_mutex.

locking/rtmutex: Squash self-deadlock check for ww_rt_mutex.

Similar to the issues in commits:

  6467822b8cc9 ("locking/rtmutex: Prevent spurious EDEADLK return caused by ww_mutexes")
  a055fcc132d4 ("locking/rtmutex: Return success on deadlock for ww_mutex waiters")

ww_rt_mutex_lock() should not return EDEADLK without first going through
the __ww_mutex logic to set the required state. In fact, the chain-walk
can deal with the spurious cycles (per the above commits) this check
warns about and is trying to avoid.

Therefore ignore this test for ww_rt_mutex and simply let things fall
in place.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20211129174654.668506-4-bigeasy@linutronix.de