apalis/colibri_imx6: use independent USB PID for SPL

Use a completely independent USB Product ID for SPL. This allows
to differentiate a SDP running in SPL and SDP running in a U-Boot
which could not read the config block successfully.

Signed-off-by: Stefan Agner <stefan.agner@toradex.com>
Acked-by: Max Krummenacher <max.krummenacher@toradex.com>
Reviewed-by: Łukasz Majewski <lukma@denx.de>