i40e: fix missed "Negotiated" string in i40e_print_link_message()

The "Negotiated" string in i40e_print_link_message() function was missed.
This string has been added to the dmesg and small refactoring done removing
common substrings and unifying link status message format.
Without this patch it was not clear that FEC is related to negotiated FEC.

Signed-off-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>