Following omap3-evm.dts way, it changes all imx dts files to use label
in board dts to refer to nodes defined by soc dtsi.  Thus, the board
dts files become easier to read and edit with the least indentation
levels.
Signed-off-by: NShawn Guo <shawn.guo@linaro.org>

This adds a i.MX25 dtsi file along with the i.MX25 clock tree
documentation. The devicetree should be fairly complete for:

- uart
- fec
- i2c
- spi
- pwm
- nand
- gpio
- wdog
- esdhc
- flexcan

The more exotic devices currently miss clock bindings.
Signed-off-by: NSascha Hauer <s.hauer@pengutronix.de>
Acked-by: NShawn Guo <shawn.guo@linaro.org>