enetc: Force correct order with DRIVER_MODULE_ORDERED

The toolchain can reorder symbols, meaning that changing
the order of DRIVER_MODULE macros is not enough
to ensure that miibus gets registered first.
Use DRIVER_MODULE_ORDERED instead to fix the problem properly.

Fixes: 5ad6d28cbe6b ("enetc: Support building the driver as a loadable module.")

Reported by: jhb