locking/rtmutex: Remove rtmutex deadlock tester leftovers

The following debug members of 'struct rtmutex' are unused:

 - save_state: No users

 - file,line: Printed if ::name is NULL. This is only used for non-futex
	      locks so ::name is never NULL

 - magic:     Assigned to NULL by rt_mutex_destroy(), no further usage

Remove them along with unused inline and macro leftovers related to
the long gone deadlock tester.

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/20210326153943.195064296@linutronix.de