MAINTAINERS: change colibri_imx6/imx6ull/t30/vf maintainers

Take over maintainership for colibri_imx6/imx6ull/t30/vf modules.

Signed-off-by: Igor Opaniuk <igor.opaniuk@toradex.com>
Acked-by: Max Krummenacher <max.krummenacher@toradex.com>
Acked-by: Stefan Agner <stefan.agner@toradex.com>