ARM: dts: imx6qdl-colibri: Add missing pin declaration in iomuxc

This adds the muxing for the optional pins usb-oc (overcurrent) and
usb-id.

Signed-off-by: Philippe Schenker <philippe.schenker@toradex.com>
Acked-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>