Install a temporary workaround to avoid problems in fdt data with linux's
workaround for an imx6 chip erratum.  Linux works around the bug with
changes in fdt data that we can't currently handle, so to enable running
with standard vendor-supplied fdt data, this watches for an attempt to map
the gpio1_6 interrupt and remaps it back to the standard ethernet interrupt.

This can be undone when the intrng project is completed and our gpio drivers
can also be interrupt controllers.