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/clk/Makefile b/drivers/clk/Makefile
index f87c9ae..821b586 100644
--- a/drivers/clk/Makefile
+++ b/drivers/clk/Makefile
@@ -1,9 +1,8 @@
+# SPDX-License-Identifier: GPL-2.0+
 #
 # Copyright (c) 2015 Google, Inc
 # Wolfgang Denk, DENX Software Engineering, wd@denx.de.
 #
-# SPDX-License-Identifier:      GPL-2.0+
-#
 
 obj-$(CONFIG_$(SPL_TPL_)CLK) += clk-uclass.o clk_fixed_rate.o