eth: fbnic: add support for TTI HW stats

Add coverage for the TX Extension (TEI) Interface (TTI) stats. We are
tracking packets and control message drops because of credit exhaustion
on the TX interface.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Mohsin Bashir <mohsin.bashr@gmail.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250410070859.4160768-6-mohsin.bashr@gmail.com


Signed-off-by: Paolo Abeni <pabeni@redhat.com>