ARM: dts: imx25.dtsi: change the clock information for usb

For imx25, it needs three clocks to let the controller work,
the old code is wrong, and usbmisc has not included clock
handling code any more.

Tested-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Peter Chen <peter.chen@freescale.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>