sched: Introduce task_is_running()

Replace a bunch of 'p->state == TASK_RUNNING' with a new helper:
task_is_running(p).

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Davidlohr Bueso <dave@stgolabs.net>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20210611082838.222401495@infradead.org

arch/h8300/kernel/process.c

@@ -134,7 +134,7 @@ unsigned long get_wchan(struct task_struct *p)
 	unsigned long stack_page;
 	int count = 0;
 
-	if (!p || p == current || p->state == TASK_RUNNING)
+	if (!p || p == current || task_is_running(p))
 		return 0;
 
 	stack_page = (unsigned long)p;