mxs: do not unconditionally enable clock output to pad

Signed-off-by: Michael Heimpold <mhe@iequalize.de>
Home-Box: add define for REV0300

Signed-off-by: Michael Heimpold <mhe@iequalize.de>
Home-Box: HW3 REV0300 has external crystal for enet

Signed-off-by: Michael Heimpold <mhe@iequalize.de>
Home-Box: fix netconsole

- resetting environment to serial console not necessary as it
  defaults to serial after reboot
- disable netconsole by default for SoM test during manufacturing

Signed-off-by: Michael Heimpold <mhe@iequalize.de>