drivers: cosmetic: Convert SPDX license tags to Linux Kernel style

Complete in the drivers directory the work started with
commit 83d290c56fab ("SPDX: Convert all of our single
license tags to Linux Kernel style").

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
diff --git a/drivers/usb/common/Makefile b/drivers/usb/common/Makefile
index aee7e32..55e0547 100644
--- a/drivers/usb/common/Makefile
+++ b/drivers/usb/common/Makefile
@@ -1,6 +1,6 @@
-# (C) Copyright 2016 Freescale Semiconductor, Inc.
+# SPDX-License-Identifier: GPL-2.0+
 #
-# SPDX-License-Identifier:      GPL-2.0+
+# (C) Copyright 2016 Freescale Semiconductor, Inc.
 #
 
 obj-$(CONFIG_DM_USB) += common.o