libavb: Update SPDX tag style

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/lib/libavb/Makefile b/lib/libavb/Makefile
index c8ff080..b983fe7 100644
--- a/lib/libavb/Makefile
+++ b/lib/libavb/Makefile
@@ -1,8 +1,6 @@
+# SPDX-License-Identifier: GPL-2.0+
 #
 # (C) Copyright 2017 Linaro Limited
-#
-# SPDX-License-Identifier:	GPL-2.0+
-#
 
 obj-$(CONFIG_LIBAVB) += avb_chain_partition_descriptor.o avb_cmdline.o
 obj-$(CONFIG_LIBAVB) += avb_crypto.o avb_footer.o avb_hashtree_descriptor.o