mm/zsmalloc: add missing annotation for migrate_read_unlock()

Sparse reports a warning at migrate_read_unlock()()

 warning: context imbalance in migrate_read_unlock() - unexpected unlock

The root cause is the missing annotation at migrate_read_unlock()
Add the missing __releases(&zspage->lock) annotation

Signed-off-by: Jules Irenge <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Acked-by: Minchan Kim <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>

mm/zsmalloc.c

@@ -1838,7 +1838,7 @@ static void migrate_read_lock(struct zspage *zspage) __acquires(&zspage->lock)
 	read_lock(&zspage->lock);
 }
 
-static void migrate_read_unlock(struct zspage *zspage)
+static void migrate_read_unlock(struct zspage *zspage) __releases(&zspage->lock)
 {
 	read_unlock(&zspage->lock);
 }