Since it is needed outside usbcore and exposed in include/linux/usb.h,
it conflicts with enum dev_state in rt2x00 wireless driver.

Mark it as usb specific to avoid conflicts in the future.
Signed-off-by: NValentina Manea <valentina.manea.m@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>