niu: Change niu_rbr_fill() to use unlikely() to check niu_rbr_add_page() return value

Change niu_rbr_fill() to use unlikely() to check niu_rbr_add_page() return
value to be consistent with the rest of the checks after niu_rbr_add_page()
calls in this file.
Signed-off-by: NShuah Khan <shuah.khan@hp.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/sun/niu.c

@@ -3517,7 +3517,7 @@ static int niu_rbr_fill(struct niu *np, struct rx_ring_info *rp, gfp_t mask)
 	err = 0;
 	while (index < (rp->rbr_table_size - blocks_per_page)) {
 		err = niu_rbr_add_page(np, rp, mask, index);
-		if (err)
+		if (unlikely(err))
 			break;
 
 		index += blocks_per_page;