ARM: dts: imx6ul-pico-hobbit: Fix Ethernet PHY reset GPIO

According to the imx6ul-pico-hobbit schematics the Ethernet PHY reset GPIO
is GPIO1_28, so fix it accordingly.

Also adjust the reset duration to 1ms, because the KSZ8081 datasheet
requires 500μs.

Signed-off-by: Diego Dorta <diego.dorta@nxp.com>
Reviewed-by: Fabio Estevam <fabio.estevam@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>