staging: bcm2835-camera: Restore return behavior of ctrl_set_bitrate()

The commit 52c4dfcead ("Staging: vc04_services: Cleanup in
ctrl_set_bitrate()") changed the return behavior of ctrl_set_bitrate().
We cannot do this because of a bug in the firmware, which breaks probing
of bcm2835-camera:

    bcm2835-v4l2: mmal_init: failed to set all camera controls: -3
    Cleanup: Destroy video encoder
    Cleanup: Destroy image encoder
    Cleanup: Destroy video render
    Cleanup: Destroy camera
    bcm2835-v4l2: bcm2835_mmal_probe: mmal init failed: -3
    bcm2835-camera: probe of bcm2835-camera failed with error -3

So restore the old behavior, add an explaining comment and a debug message
to verify that the bug has been fixed in firmware.

Fixes: 52c4dfcead ("Staging: vc04_services: Cleanup in ctrl_set_bitrate()")
Signed-off-by: Stefan Wahren <wahrenst@gmx.net>
Cc: stable <stable@vger.kernel.org>
Acked-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/vc04_services/bcm2835-camera/controls.c

@@ -604,15 +604,28 @@ static int ctrl_set_bitrate(struct bm2835_mmal_dev *dev,
 			    struct v4l2_ctrl *ctrl,
 			    const struct bm2835_mmal_v4l2_ctrl *mmal_ctrl)
 {
+	int ret;
 	struct vchiq_mmal_port *encoder_out;
 
 	dev->capture.encode_bitrate = ctrl->val;
 
 	encoder_out = &dev->component[MMAL_COMPONENT_VIDEO_ENCODE]->output[0];
 
-	return vchiq_mmal_port_parameter_set(dev->instance, encoder_out,
-					     mmal_ctrl->mmal_id, &ctrl->val,
-					     sizeof(ctrl->val));
+	ret = vchiq_mmal_port_parameter_set(dev->instance, encoder_out,
+					    mmal_ctrl->mmal_id, &ctrl->val,
+					    sizeof(ctrl->val));
+
+	v4l2_dbg(1, bcm2835_v4l2_debug, &dev->v4l2_dev,
+		 "%s: After: mmal_ctrl:%p ctrl id:0x%x ctrl val:%d ret %d(%d)\n",
+		 __func__, mmal_ctrl, ctrl->id, ctrl->val, ret,
+		 (ret == 0 ? 0 : -EINVAL));
+
+	/*
+	 * Older firmware versions (pre July 2019) have a bug in handling
+	 * MMAL_PARAMETER_VIDEO_BIT_RATE that result in the call
+	 * returning -MMAL_MSG_STATUS_EINVAL. So ignore errors from this call.
+	 */
+	return 0;
 }
 
 static int ctrl_set_bitrate_mode(struct bm2835_mmal_dev *dev,