ARM: dts: colibri: introduce device trees with UHS-I support

1. Introduce dtsi with overlay configuration for enabling UHS-I
for Colibri iMX6S/DL V1.1x re-design.
2. Introduce new dts for the Colibri iMX6S/DL V1.1x
on Colibri Evaluation Carrier Board V3.x. However, disable 1.8V for
the Colibri Evaluation Board since this carrier board has 3.3V pull-ups on.
3. Provide proper configuration for VGEN3, which allows that rail to
be automatically switched to 1.8 volts for proper UHS-I operation mode.

Signed-off-by: Igor Opaniuk <igor.opaniuk@toradex.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>