ARM: dts: add dtsi for imx6q and imx6dl

Add dtsi for imx6q and imx6dl with non-common blocks moved into there.
Major differences between imx6dl and imx6q:

 * Dual vs. Quad cores
 * single vs. dual IPU
 * 128 vs. 256 KB OCRAM
 * imx6q: ECSPI5, OpenVG (GC355), SATA
 * imx6dl: I2C4, PXP, EPDC, LCDIF
 * iomuxc/pads definition

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