Add the ability in the vxge driver to flash firmware via ethtool.

Updated to include comments from Ben Hutchings.
Signed-off-by: NJon Mason <jon.mason@exar.com>
Signed-off-by: NRam Vepa <ram.vepa@exar.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>