tg3: Fix for diasllow rx coalescing time to be 0

When the rx coalescing time is 0, interrupts
are not generated from the controller and rx path hangs.
To avoid this rx hang, updating the driver to not allow
rx coalescing time to be 0.
Signed-off-by: NSatish Baddipadige <satish.baddipadige@broadcom.com>
Signed-off-by: NSiva Reddy Kallam <siva.kallam@broadcom.com>
Signed-off-by: NMichael Chan <michael.chan@broadcom.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/broadcom/tg3.c

@@ -14014,6 +14014,7 @@ static int tg3_set_coalesce(struct net_device *dev, struct ethtool_coalesce *ec)
 	}
 
 	if ((ec->rx_coalesce_usecs > MAX_RXCOL_TICKS) ||
+	    (!ec->rx_coalesce_usecs) ||
 	    (ec->tx_coalesce_usecs > MAX_TXCOL_TICKS) ||
 	    (ec->rx_max_coalesced_frames > MAX_RXMAX_FRAMES) ||
 	    (ec->tx_max_coalesced_frames > MAX_TXMAX_FRAMES) ||