usb: chipidea: udc: using structure ci_hdrc device for runtime PM

At current code, it doesn't maintain ci->gadget.dev's runtime PM
status well, eg, during the PM operation, the PM counter for
ci->gadget.dev doesn't be changed accordingly.

In this commit, we use ci_hdrc device instead of ci->gadget.dev
for runtime PM APIs at udc driver, in the way, we handle runtime
PM APIs using unify device structure between core and udc driver.

Reviewed-by: Jun Li <jun.li@nxp.com>
Signed-off-by: Peter Chen <peter.chen@nxp.com>