ARM: dts: add more imx6q/dl pin groups

Add more imx6q/dl pin groups for those supported boards, e.g. sabresd,
sabreauto, arm2.

IPU2 pin groups are added into imx6q.dtsi, since the block is only
available on imx6q.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>