ARM: dts: vf610: Add usbmisc for non-core registers

Add device tree node for usbmisc which controls the non-core USB
registers. This is required to use the property to disable the over-
current detection.

Signed-off-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Shawn Guo <shawn.guo@freescale.com>