bus/fsl_mc: Do not rely on caller to provide non NULL mc_io

Before destroying the mc_io, check first that it was
allocated.
Reviewed-by: Laurentiu Tudor <laurentiu.tudor@nxp.com>
Acked-by: Laurentiu Tudor <laurentiu.tudor@nxp.com>
Signed-off-by: Diana Craciun <diana.craciun@oss.nxp.com>
Link: https://lore.kernel.org/r/20200929085441.17448-11-diana.craciun@oss.nxp.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/bus/fsl-mc/mc-io.c

@@ -129,7 +129,12 @@ int __must_check fsl_create_mc_io(struct device *dev,
  */
 void fsl_destroy_mc_io(struct fsl_mc_io *mc_io)
 {
-	struct fsl_mc_device *dpmcp_dev = mc_io->dpmcp_dev;
+	struct fsl_mc_device *dpmcp_dev;
+
+	if (!mc_io)
+		return;
+
+	dpmcp_dev = mc_io->dpmcp_dev;
 
 	if (dpmcp_dev)
 		fsl_mc_io_unset_dpmcp(mc_io);