sched: Remove stale PF_MUTEX_TESTER bit

commit 15917dc02841862840efcbfe1da0830f88078b5c upstream.

The RTMUTEX tester was removed long ago but the PF bit stayed
around. Remove it and free up the space.
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Signed-off-by: NJoseph Qi <joseph.qi@linux.alibaba.com>
Reviewed-by: NXiaoguang Wang <xiaoguang.wang@linux.alibaba.com>

include/linux/sched.h

@@ -1456,7 +1456,6 @@ extern struct pid *cad_pid;
 #define PF_MEMSTALL		0x01000000	/* Stalled due to lack of memory */
 #define PF_NO_SETAFFINITY	0x04000000	/* Userland is not allowed to meddle with cpus_allowed */
 #define PF_MCE_EARLY		0x08000000      /* Early kill for mce process policy */
-#define PF_MUTEX_TESTER		0x20000000	/* Thread belongs to the rt mutex tester */
 #define PF_FREEZER_SKIP		0x40000000	/* Freezer should not count it as freezable */
 #define PF_SUSPEND_TASK		0x80000000      /* This thread called freeze_processes() and should not be frozen */