net/macb: add the user i/o to ethtool register dump

User i/o register EMAC_USRIO or GMAC_UR can be found on both macb and gem
flavors of the peripheral. By using the proper accessor, we can add it to the
register dump feature of ethtool.
Increment the version of this API so it can be noticed from user space.

Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>