dpaa2-mac: remove an unnecessary check

The dpaa2-eth driver has phylink integration only if the connected dpmac
object is in TYPE_PHY (aka the PCS/PHY etc link status is managed by
Linux instead of the firmware). The check is thus unnecessary because
the code path that reaches the .mac_link_up() callback is only with
TYPE_PHY dpmac objects.

Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>