dts: usb: Add no-voltage-regulator property to nxp,kinetis-usbd binding

Some NXP SoC's do not have USB voltage regulator present.
Add property to indicate it. Negative logic is used, because
the regulator is present in great majority of SoC's, and thus the new
property can be added only for SoC's without the regulator.

Signed-off-by: Michal Smola <michal.smola@nxp.com>