ARM: dts: imx6ul-14x14-evk: Describe the KSZ8081 reset

ARM: dts: imx6ul-14x14-evk: Describe the KSZ8081 reset

There are two KSZ8081 on the imx6ul-14x14-evk: one has the reset line
controlled by the Q1 output of the 74LV595PW expander, and the other
by the Q2 output.

The KSZ8081 datasheet states that the tsr parameter (Stable supply
voltage (VDDIO, VDDA_3.3) to reset high) to be 10ms minimum and
"After the de-assertion of reset, wait a minimum of 100 µs before
starting programming on the MIIM (MDC/MDIO) interface."

Describe these parameters in the devicetree.

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>