toradex: apply u-boot and flashing script changes to colibri-imx7

Add required changes to colibri-imx7 configs after the u-boot and
flashing script change was merged from fido branch.

Change-Id: Id01d311490f1b7a62994f914852a820a10ad7ddc
Reviewed-by: Risto Avila <risto.avila@qt.io>
Reviewed-by: Teemu Holappa <teemu.holappa@theqtcompany.com>