These functions allows to deactivate gadget to make it not visible to
host and make it active again when gadget driver is finally ready.
They are needed to fix usb_function_activate() and usb_function_deactivate()
functions which currently are not working as usb_gadget_connect() is
called immediately after function bind regardless to previous calls of
usb_gadget_disconnect() function.
Signed-off-by: Robert Baldyga <r.baldyga@samsung.com> Signed-off-by: Felipe Balbi <balbi@ti.com>