hw/net/xilinx_ethlite: Map the RAM buffer as RAM memory region

hw/net/xilinx_ethlite: Map the RAM buffer as RAM memory region

Rather than using I/O registers for RAM buffer, having to
swap endianness back and forth (because the core memory layer
automatically swaps endiannes for us), declare the buffers
as RAM regions. The "xlnx.xps-ethernetlite" MR doesn't have
any more I/O regions. Remove the now unused s->regs[] array.

The memory flat view becomes:

  FlatView #0
   Root memory region: system
    0000000081000000-00000000810007e3 (prio 0, ram): ethlite.tx[0]buf
    00000000810007e4-00000000810007f3 (prio 0, i/o): ethlite.mdio
    00000000810007f4-00000000810007ff (prio 0, i/o): ethlite.tx[0]io
    0000000081000800-0000000081000fe3 (prio 0, ram): ethlite.tx[1]buf
    0000000081000ff4-0000000081000fff (prio 0, i/o): ethlite.tx[1]io
    0000000081001000-00000000810017e3 (prio 0, ram): ethlite.rx[0]buf
    00000000810017fc-00000000810017ff (prio 0, i/o): ethlite.rx[0]io
    0000000081001800-0000000081001fe3 (prio 0, ram): ethlite.rx[1]buf
    0000000081001ffc-0000000081001fff (prio 0, i/o): ethlite.rx[1]io

Reported-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@amd.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-Id: <20241114210010.34502-18-philmd@linaro.org>