dpaa2-eth: use new PTP_MSGTYPE_* define(s)

Remove usage of magic numbers.

Signed-off-by: Christian Eggers <ceggers@arri.de>
Cc: Ioana Ciornei <ioana.ciornei@nxp.com>
Cc: Ioana Radulescu <ruxandra.radulescu@nxp.com>
Cc: Yangbo Lu <yangbo.lu@nxp.com>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Reviewed-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>