ARM: dts: imx6-tx6: improve ethernet related pinctrl setup

Remove the PHY INT and RESET pins from hog section and put them into
their own pinctrl nodes referenced by the appropriate driver nodes.
Also, the MDIO pins are required for probing the Ethernet PHY, so they
must be configured by the FEC driver, not by the PHY driver. Move the
corresponding pinctrl settings from the PHY subnode to the FEC node.

Signed-off-by: Lothar Waßmann <LW@KARO-electronics.de>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>