ARM: dts: imx6ull-colibri: add support for toradex aster carrier boards

Add support for Toradex Aster, small form-factor Colibri Arm
Computer Module family carrier board.

Aster Device Trees:
- imx6ull-colibri-aster.dtb
- imx6ull-colibri-emmc-aster.dtb
- imx6ull-colibri-wifi-aster.dtb

Signed-off-by: Denys Drozdov <denys.drozdov@toradex.com>
Signed-off-by: Marcel Ziswiler <marcel.ziswiler@toradex.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>