i40e: Move error message to debug level

There is an error coming back from get_phy_capabilities that does not
seem to have any functional implications. We will continue looking into
why this error message is occurring, but in the meantime, we will move it
to debug to avoid confusion.

Change-ID: I9091754bf62c066ddedeb249923d85606e2d68ed
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>