novena: Fix ethernet PHY reset sequence

This patch fixes conflict between PHY pins becoming outputs after reset and
imx6 still driving the pins. It also fixes the reset timing as recommended by
the PHY datasheet.

Signed-off-by: Nikolay Dimitrov <picmaster@mail.bg>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Sean Cross <xobs@kosagi.com>
Cc: Marek Vasut <marex@denx.de>
Reviewed-by: Fabio Estevam <fabio.estevam@freescale.com>