net: stmmac: fix a broken u32 less than zero check

The check that queue is less or equal to zero is always true
because queue is a u32; queue is decremented and will wrap around
and never go -ve. Fix this by making queue an int.

Detected by CoverityScan, CID#1428988 ("Unsigned compared against 0")
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

@@ -1208,7 +1208,7 @@ static int init_dma_rx_desc_rings(struct net_device *dev, gfp_t flags)
 	u32 rx_count = priv->plat->rx_queues_to_use;
 	unsigned int bfsize = 0;
 	int ret = -ENOMEM;
-	u32 queue;
+	int queue;
 	int i;
 
 	if (priv->hw->mode->set_16kib_bfsize)