According to the Zynq TRM, gigabit half duplex is not supported.  Add a
new cap and compatible string so Zynq can avoid advertising that mode.
Signed-off-by: NNathan Sullivan <nathan.sullivan@ni.com>
Acked-by: NNicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>