arm64: dts: meson: g12b: odroid-n2: fix PHY deassert timing requirements

According to the datasheet (Rev. 1.9) the RTL8211F requires at least
72ms "for internal circuits settling time" before accessing the PHY
registers. This fixes an issue where the Ethernet link doesn't come up
when using ip link set down/up:
  [   29.360965] meson8b-dwmac ff3f0000.ethernet eth0: Link is Down
  [   34.569012] meson8b-dwmac ff3f0000.ethernet eth0: PHY [0.0:00] driver [RTL8211F Gigabit Ethernet] (irq=31)
  [   34.676732] meson8b-dwmac ff3f0000.ethernet: Failed to reset the dma
  [   34.678874] meson8b-dwmac ff3f0000.ethernet eth0: stmmac_hw_setup: DMA engine initialization failed
  [   34.687850] meson8b-dwmac ff3f0000.ethernet eth0: stmmac_open: Hw setup failed

Fixes: 658e4129 ("arm64: dts: meson: g12b: odroid-n2: add the Ethernet PHY reset line")
Reviewed-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>
Link: https://lore.kernel.org/r/df3f5c4fc6e43c55429fd3662a636036a21eed49.1607363522.git.stefan@agner.ch