MFC 292409:

It seems certain Intel GPUs use GPIO bitbanging over a child device
instead of GMBUS access for I2C transfers.  The GMBUS driver falls back
to this mode when a transfer times out.  However, the first transfer to
timeout was sending the request back to itself resulting in an panic due
to recursing on a lock.  Fix it to forward the request on to the proper
device.  This appears to have been accidentally changed in r277487.

sys/dev/drm2/i915/intel_iic.c

@@ -467,8 +467,7 @@ timeout:
 	 * Try GPIO bitbanging instead.
 	 */
 	sc->force_bit_dev = true;
-	error = -IICBUS_TRANSFER(idev, msgs, nmsgs);
-	goto out;
+	error = -IICBUS_TRANSFER(dev_priv->bbbus[unit], msgs, nmsgs);
 
 out:
 	sx_xunlock(&dev_priv->gmbus_sx);