usb: chipidea: core: add sysfs group

Sometimes, the user needs to adjust some properties for controllers, eg
the role for controller, we add sysfs group for them.

The attribute 'role' is used to switch host/gadget role dynamically, the
uewr can read the current role, and write the other role compare to
current one to finish the switch.

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