dts: nxp: Convert ENET DT default to new binding.

Convert all of the NXP SOCs with ENET to use the new
binding scheme, which is used by the new driver.

Convert any boards using this SOC to the new scheme as well,
and remove from the documentation the bit about the experimental
nature of the new driver and the overlay that shall no longer exist.

Some of the boards I do not have the hardware of, so apologies
if something breaks, as I have no way to know. All the boards
were made sure to at least build.

Signed-off-by: Declan Snyder <declan.snyder@nxp.com>