locking/mutex: Fix non debug version of mutex_lock_io_nested()

If CONFIG_DEBUG_LOCK_ALLOC=n then mutex_lock_io_nested() maps to
mutex_lock() which is clearly wrong because mutex_lock() lacks the
io_schedule_prepare()/finish() invocations.

Map it to mutex_lock_io().

Fixes: f21860ba

 ("locking/mutex, sched/wait: Fix the mutex_lock_io_nested() define")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/878s6fshii.fsf@nanos.tec.linutronix.de