ixgbe: fix older devices that do not support IXGBE_MRQC_L3L4TXSWEN

The enabling L3/L4 filtering for transmit switched packets for all
devices caused unforeseen issue on older devices when trying to send UDP
traffic in an ordered sequence.  This bit was originally intended for X550
devices, which supported this feature, so limit the scope of this bit to
only X550 devices.

Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>