mm/mmap.c: replace IS_ERR and PTR_ERR with PTR_ERR_OR_ZERO

Fix a coccinelle error regarding usage of IS_ERR and PTR_ERR instead of
PTR_ERR_OR_ZERO.
Signed-off-by: Duan Jiong <duanj.fnst@cn.fujitsu.com>
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/mmap.c

@@ -2965,9 +2965,7 @@ int install_special_mapping(struct mm_struct *mm,
 	struct vm_area_struct *vma = _install_special_mapping(mm,
 			    addr, len, vm_flags, pages);
 
-	if (IS_ERR(vma))
-		return PTR_ERR(vma);
-	return 0;
+	return PTR_ERR_OR_ZERO(vma);
 }
 
 static DEFINE_MUTEX(mm_all_locks_mutex);