doc: usb: ci-hdrc-usb2: Add pinctrl properties for HSIC pin groups

For USB HSIC, the data and strobe pin needs to be pulled down
at default, we consider it as "idle" state. When the USB host
is ready to be used, the strobe pin needs to be pulled up,
we consider it as "active" state.

Signed-off-by: Peter Chen <peter.chen@nxp.com>