include/linux/mm.h: return true in cpupid_pid_unset()

Fix the following coccicheck warning:

  include/linux/mm.h:1371:8-9: WARNING: return of 0/1 in function 'cpupid_pid_unset' with return type bool

Signed-off-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/20200422071816.48879-1-yanaijie@huawei.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/mm.h

@@ -1373,7 +1373,7 @@ static inline int cpu_pid_to_cpupid(int nid, int pid)
 
 static inline bool cpupid_pid_unset(int cpupid)
 {
-	return 1;
+	return true;
 }
 
 static inline void page_cpupid_reset_last(struct page *page)