i40e: Add support for 'ethtool -m'

This patch adds support for 'ethtool -m' command which displays
information about (Q)SFP+ module plugged into NIC's cage.

Signed-off-by: Filip Sadowski <filip.sadowski@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>