PCI: Add two more values for PCIe Max_Read_Request_Size

This patch adds missing values for the max read request size.
E.g. network driver r8169 uses a value of 4K.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>