libie: add adminq helper for converting err to str

Add a new module for common handling of Admin Queue related logic.
Start by a helper for error to string conversion. This lives inside
libie/, but is a separate module what follows our logic of splitting
into topical modules, to avoid pulling in not needed stuff, and have
better organization in general.

Olek suggested how to better solve the error to string conversion.

It will be used in follow-up patches in ice, i40e and iavf.

Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Suggested-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Signed-off-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>