dt-bindings: usb: ci-hdrc-usb2: add property power-active-high

The i.MX USB controller may drive the usb power line directly, but the
polarity depends on the board. Reset state of the polarity is low-active so
add this property to allow it to be high-active.

Signed-off-by: Philipp Puschmann <philipp.puschmann@emlix.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Peter Chen <peter.chen@nxp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>