ARM: dts: imx6ull: add imx6ull support

It is the 10th processor in the well-known imx6 series, and derived
from imx6ul but cost optimized. The more information about imx6ull
can be found at:

http://www.nxp.com/products/microcontrollers-and-processors/


arm-processors/i.mx-applications-processors/i.mx-6-processors
/i.mx6qp/i.mx-6ull-single-core-processor-with-arm-cortex-a7-core
:i.MX6ULL

imx6ul.dtsi is the SoC common stuff for both imx6ul and imx6ull;
imx6ul-14x14-evk.dts is the board common stuff for both imx6ul
and imx6ull 14x14 evk. In this patch, for SoC part, the
imx6ull.dtsi includes imx6ul.dtsi; for board part, imx6ull-14x14-evk.dts
includes imx6ul-14x14-evk.dts.

Signed-off-by: Peter Chen <peter.chen@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>