drivers: nxp_s32_netc: fix init priorities

So far the init priories were:
enetc_psi0=60 < enetc_vsin=61 < emdio=70 < ethernet-phy=80
because the Ethernet PSI driver was doing global initialization for the
whole NETC complex, including enabling MDIO function (due to the way
the HAL works).

Change to use the default init priorities:
mdio=60 < phy=70 < eth=enetc_psi0=80 < enetc_vsin=81
by executing at an early stage the NETC global initialization. This also
allows to match the DT hierarchy representation of NETC with the
effective priorities assigned.

Signed-off-by: Manuel Argüelles <manuel.arguelles@nxp.com>