ethtool: Extend ethtool plugin module eeprom API to phylib

This patch extends the ethtool plugin module eeprom API to support cards
whose phy support is delegated to a separate driver.

The handlers for ETHTOOL_GMODULEINFO and ETHTOOL_GMODULEEEPROM call the
module_info and module_eeprom functions if the phy driver provides them;
otherwise the handlers call the equivalent ethtool_ops functions provided
by network drivers with built-in phy support.

Signed-off-by: Ed Swierk <eswierk@skyportsystems.com>
Signed-off-by: David S. Miller <davem@davemloft.net>