usb: rework attach/detach workflow Add separate detach callback to USBPortOps, split uhci/ohci/musb/usbhub attach functions into two. Move common code to the usb_attach() function, only the hardware-specific bits remain in the attach/detach callbacks. Keep track of the port it is attached to for each usb device. [ v3: fix tyops in usb-musb.c ] Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>