Update config files : build PHYLIB as a module.
    
    All but armv7hl/cubox: make PHYLIB modular. Most systems don't
    need it, and it registers a mdio_bus driver. As a side effect,
    we have to disable PHY emulation support, as it is only availble
    when PHYLIB is built-in. This driver is rather weird anyway and
    hopefully no system we want to support needs it, so it should be
    OK.
     - CONFIG_PHYLIB=m
     - CONFIG_FIXED_PHY=n