[][kernel][mt7986][eth][Refactor external PHY0 DTS configuratoin]

[Description]
Refactor external PHY0 DTS configuratoin.

Move phy-handle of external PHY0 to lan5(switch port5) to meet RFB topology.

[Release-log]
N/A

Change-Id: I5d2ce72159a5824335bb32499168e5eb5191a412
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/6398255
9 files changed