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/ram/rockchip/Makefile b/drivers/ram/rockchip/Makefile
index 1a1e557..5df1960 100644
--- a/drivers/ram/rockchip/Makefile
+++ b/drivers/ram/rockchip/Makefile
@@ -1,8 +1,7 @@
+# SPDX-License-Identifier: GPL-2.0+
 #
 # Copyright (c) 2017 Theobroma Systems Design und Consulting GmbH
 #
-# SPDX-License-Identifier:      GPL-2.0+
-#
 
 obj-$(CONFIG_ROCKCHIP_RK3368) = dmc-rk3368.o
 obj-$(CONFIG_ROCKCHIP_RK3128) = sdram_rk3128.o