spi: Unlock a spinlock before calling into the controller driver.

spi_pump_messages() calls into a controller driver with
unprepare_transfer_hardware() which is documented as "This may sleep".
As in the prepare_transfer_hardware() call below, we should release the
queue_lock spinlock before making the call.
Rework the logic a bit to hold queue_lock to protect the 'busy' flag,
then release it to call unprepare_transfer_hardware().
Signed-off-by: Bryan Freed <bfreed@chromium.org>
Reviewed-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Doug Anderson <dianders@chromium.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

drivers/spi/spi.c

@@ -543,17 +543,16 @@ static void spi_pump_messages(struct kthread_work *work)
 	/* Lock queue and check for queue work */
 	spin_lock_irqsave(&master->queue_lock, flags);
 	if (list_empty(&master->queue) || !master->running) {
-		if (master->busy && master->unprepare_transfer_hardware) {
-			ret = master->unprepare_transfer_hardware(master);
-			if (ret) {
+		if (!master->busy) {
 			spin_unlock_irqrestore(&master->queue_lock, flags);
-				dev_err(&master->dev,
-					"failed to unprepare transfer hardware\n");
 			return;
 		}
-		}
 		master->busy = false;
 		spin_unlock_irqrestore(&master->queue_lock, flags);
+		if (master->unprepare_transfer_hardware &&
+		    master->unprepare_transfer_hardware(master))
+			dev_err(&master->dev,
+				"failed to unprepare transfer hardware\n");
 		return;
 	}