Add links to the IEEE 802.3-2008 document, and the RGMII v1.3 and v2.0
revisions of the standard.
Reviewed-by: NMartin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: NFlorian Fainelli <f.fainelli@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>