sched/headers: Remove <linux/rtmutex.h> from <linux/sched.h>

This reduces header dependencies.
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

include/linux/sched.h

@@ -16,7 +16,6 @@
 #include <linux/pid.h>
 #include <linux/seccomp.h>
 #include <linux/rculist.h>
-#include <linux/rtmutex.h>
 
 #include <linux/resource.h>
 #include <linux/hrtimer.h>