sched: Add snapshot of Window Assisted Load Tracking (WALT)

This snapshot is taken from msm-4.19 as of commit 5debecbe7195
("trace: filter out spurious preemption and IRQs disable traces").

Change-Id: I8fab4084971baadcaa037f40ab549fc073a4b1ea
Signed-off-by: Satya Durga Srinivasu Prabhala <satyap@codeaurora.org>

kernel/exit.c

@@ -761,6 +761,7 @@ void __noreturn do_exit(long code)
 	}
 
 	exit_signals(tsk);  /* sets PF_EXITING */
+	sched_exit(tsk);
 	/*
 	 * Ensure that all new tsk->pi_lock acquisitions must observe
 	 * PF_EXITING. Serializes against futex.c:attach_to_pi_owner().