arm64: dts: meson: 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 seen on ODROID-C2 where the Ethernet
link doesn't come up when using ip link set down/up:
  [ 6630.714855] meson8b-dwmac c9410000.ethernet eth0: Link is Down
  [ 6630.785775] meson8b-dwmac c9410000.ethernet eth0: PHY [stmmac-0:00] driver [RTL8211F Gigabit Ethernet] (irq=36)
  [ 6630.893071] meson8b-dwmac c9410000.ethernet: Failed to reset the dma
  [ 6630.893800] meson8b-dwmac c9410000.ethernet eth0: stmmac_hw_setup: DMA engine initialization failed
  [ 6630.902835] meson8b-dwmac c9410000.ethernet eth0: stmmac_open: Hw setup failed

Fixes: f29cabf2 ("arm64: dts: meson: use the generic Ethernet PHY reset GPIO bindings")
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/4a322c198b86e4c8b3dda015560a683babea4d63.1607363522.git.stefan@agner.ch