i40e: add 100Mb ethtool reporting

Add some missing reporting/advertisement of 100Mb capability
for adapters that support it.

Change-ID: I8b8523fbdc99517bec29d90c71b3744db11542ac
Signed-off-by: Catherine Sullivan <catherine.sullivan@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>