The rtmutex specific deadlock detector predates lockdep coverage of rtmutex
and since commit f5694788

 ("rt_mutex: Add lockdep annotations") it
contains a lot of redundant functionality:

 - lockdep will detect an potential deadlock before rtmutex-debug
   has a chance to do so

 - the deadlock debugging is restricted to rtmutexes which are not
   associated to futexes and have an active waiter, which is covered by
   lockdep already

Remove the redundant functionality and move actual deadlock WARN() into the
deadlock code path. The latter needs a seperate cleanup.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210326153943.320398604@linutronix.de