rtmutex: Clarify the boost/deboost part

upstream commit: a57594a13a446d1a6ab1dcd48339f799ce586843

Add a separate local variable for the boost/deboost logic to make the
code more readable. Add comments where appropriate.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

Conflicts:
	kernel/locking/rtmutex.c
1 file changed