net: fsl_enetc: Fold DT MAC address update into enetc_set_ierb_primary_mac()

net: fsl_enetc: Fold DT MAC address update into enetc_set_ierb_primary_mac()

The entire content of the loop can be folded into enetc_set_ierb_primary_mac(),
do it. This changes the behavior slightly such that the DT is only updated in
case of a LS1028A, which is the only SoC with ethernet MAC path in DT matching
"/soc/pcie@1f0000000/ethernet@%x,%x" anyway, so this slight change should have
no impact.

Signed-off-by: Marek Vasut <marex@denx.de>