arm64: dts: renesas: white-hawk-single: Improve Ethernet TSN description

arm64: dts: renesas: white-hawk-single: Improve Ethernet TSN description

  - Add the missing "ethernet3" alias for the Ethernet TSN port, so
    U-Boot will fill its local-mac-address property based on the
    "eth3addr" environment variable (if set), avoiding a random MAC
    address being assigned by the OS,
  - Rename the numerical Ethernet PHY label to "tsn0_phy", to avoid
    future conflicts, and for consistency with the "avbN_phy" labels.

Fixes: 3d8e475bd7a724a9 ("arm64: dts: renesas: white-hawk-single: Wire-up Ethernet TSN")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Link: https://lore.kernel.org/367f10a18aa196ff1c96734dd9bd5634b312c421.1746624368.git.geert+renesas@glider.be