maple tree: use goto label to simplify code

Use the underflow goto label to set the status to ma_underflow and return
NULL, as is being done elsewhere.

[[e-mail]: add newline, per Liam (and remove one, per akpm)]
Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Dev Jain <[e-mail]>
Reviewed-by: Liam R. Howlett <[e-mail]>
Reviewed-by: Wei Yang <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>

lib/maple_tree.c

···
 	if (unlikely(mas_rewalk_if_dead(mas, node, save_point)))
 		goto retry;
 
-
 	if (likely(entry))
 		return entry;
 
 	if (!empty) {
-		if (mas->index <= min) {
-			mas->status = ma_underflow;
-			return NULL;
-		}
+		if (mas->index <= min)
+			goto underflow;
 
 		goto again;
 	}