libeth: move idpf_rx_csum_decoded and idpf_rx_extracted

Structs idpf_rx_csum_decoded and idpf_rx_extracted are used both in
idpf and iavf Intel drivers. Change the prefix from idpf_* to libeth_*
and move mentioned structs to libeth's rx.h header file.

Adjust usage in idpf driver.

Suggested-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Tested-by: Rafal Romanowski <rafal.romanowski@intel.com>
Signed-off-by: Mateusz Polchlopek <mateusz.polchlopek@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>