usb: typec: ucsi: Clear pending after acking connector change

commit 8c9b3caa upstream.

It's possible that the interrupt handler for the UCSI driver signals a
connector changes after the handler clears the PENDING bit, but before
it has sent the acknowledge request. The result is that the handler is
invoked yet again, to ack the same connector change.

At least some versions of the Qualcomm UCSI firmware will not handle the
second - "spurious" - acknowledgment gracefully. So make sure to not
clear the pending flag until the change is acknowledged.

Any connector changes coming in after the acknowledgment, that would
have the pending flag incorrectly cleared, would afaict be covered by
the subsequent connector status check.

Fixes: 217504a0

 ("usb: typec: ucsi: Work around PPM losing change information")
Cc: stable <stable@vger.kernel.org>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Acked-By: Benjamin Berg <bberg@redhat.com>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20210516040953.622409-1-bjorn.andersson@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>