rtmutex: Clean up

Previous patches changed the meaning of the return value of
rt_mutex_slowunlock(); update comments and code to reflect this.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: juri.lelli@arm.com
Cc: bigeasy@linutronix.de
Cc: xlpang@redhat.com
Cc: rostedt@goodmis.org
Cc: mathieu.desnoyers@efficios.com
Cc: jdesfossez@efficios.com
Cc: bristot@redhat.com
Link: http://lkml.kernel.org/r/20170323150216.255058238@infradead.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/kernel/futex.c b/kernel/futex.c
index 414a30d..c3eebcd 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -1394,7 +1394,7 @@
 {
 	u32 uninitialized_var(curval), newval;
 	struct task_struct *new_owner;
-	bool deboost = false;
+	bool postunlock = false;
 	DEFINE_WAKE_Q(wake_q);
 	int ret = 0;
 
@@ -1455,12 +1455,13 @@
 	/*
 	 * We've updated the uservalue, this unlock cannot fail.
 	 */
-	deboost = __rt_mutex_futex_unlock(&pi_state->pi_mutex, &wake_q);
+	postunlock = __rt_mutex_futex_unlock(&pi_state->pi_mutex, &wake_q);
 
 out_unlock:
 	raw_spin_unlock_irq(&pi_state->pi_mutex.wait_lock);
 
-	rt_mutex_postunlock(&wake_q, deboost);
+	if (postunlock)
+		rt_mutex_postunlock(&wake_q);
 
 	return ret;
 }