ARM: dts: pfla02: increase phy reset duration

Increase the reset duration to ensure correct phy functionality. The
reset duration is taken from barebox commit 52fdd510de ("ARM: dts:
pfla02: use long enough reset for ethernet phy"):

  Use a longer reset time for ethernet phy Micrel KSZ9031RNX. Otherwise a
  small percentage of modules have 'transmission timeouts' errors like

  barebox@Phytec phyFLEX-i.MX6 Quad Carrier-Board:/ ifup eth0
  warning: No MAC address set. Using random address 7e:94:4d:02:f8:f3
  eth0: 1000Mbps full duplex link detected
  eth0: transmission timeout
  T eth0: transmission timeout
  T eth0: transmission timeout
  T eth0: transmission timeout
  T eth0: transmission timeout

Cc: Stefan Christ <s.christ@phytec.de>
Cc: Christian Hemp <c.hemp@phytec.de>
Signed-off-by: Marco Felsch <m.felsch@pengutronix.de>
Fixes: 3180f956

 ("ARM: dts: Phytec imx6q pfla02 and pbab01 support")
Signed-off-by: Shawn Guo <shawnguo@kernel.org>