tg3: Fix 5719 internal FIFO overflow problem

Under load, there an internal FIFO can overflow on the 5719.  The fix is
to scale back the PCIe maximum read request size based on the current
link speed and width.

Signed-off-by: Matt Carlson <mcarlson@broadcom.com>
Reviewed-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/tg3.h b/drivers/net/tg3.h
index 06a4e7e..4107036 100644
--- a/drivers/net/tg3.h
+++ b/drivers/net/tg3.h
@@ -2948,6 +2948,7 @@
 	int				pcix_cap;
 	int				pcie_cap;
 	};
+	int				pcie_readrq;
 
 	struct mii_bus			*mdio_bus;
 	int				mdio_irq[PHY_MAX_ADDR];