ARM: dts: imx25: remove imx35-sdma compatible

The preloaded script addresses on imx25 and imx35 are different, so
imx25 is not compatible with imx35-sdma unless a custom firmware is
loaded.

Signed-off-by: Markus Pargmann <mpa@pengutronix.de>
Signed-off-by: Shawn Guo <shawn.guo@freescale.com>