BACKPORT: FROMGIT: usb: dwc3: gadget: Avoid starting DWC3 gadget during UDC unbind

There is a race present where the DWC3 runtime resume runs in parallel
to the UDC unbind sequence.  This will eventually lead to a possible
scenario where we are enabling the run/stop bit, without a valid
composition defined.

Thread#1 (handling UDC unbind):
usb_gadget_remove_driver()
-->usb_gadget_disconnect()
  -->dwc3_gadget_pullup(0)
--> continue UDC unbind sequence
-->Thread#2 is running in parallel here

Thread#2 (handing next cable connect)
__dwc3_set_mode()
  -->pm_runtime_get_sync()
    -->dwc3_gadget_resume()
      -->dwc->gadget_driver is NOT NULL yet
      -->dwc3_gadget_run_stop(1)
      --> _dwc3gadget_start()
...

Fix this by tracking the pullup disable routine, and avoiding resuming
of the DWC3 gadget.  Once the UDC is re-binded, that will trigger the
pullup enable routine, which would handle enabling the DWC3 gadget.

Acked-by: Felipe Balbi <balbi@kernel.org>
Signed-off-by: Wesley Cheng <wcheng@codeaurora.org>
Link: https://lore.kernel.org/r/20210917021852.2037-1-wcheng@codeaurora.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Bug: 200287549
(cherry picked from commit 8217f07a
 https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git

 usb-testing)
[wcheng: Fixed KMI breakage by moving softconnect to a new parent structure]
Change-Id: I9554933826710cc68136b08176290584f9ab74df
Signed-off-by: Wesley Cheng <wcheng@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>