avb: move SPDX license identifiers to the first line

Move SPDX license identifiers to the first line, so it conforms
to license placement rule [1]:

Placement:
The SPDX license identifier in kernel files shall be added at the first
possible line in a file which can contain a comment.  For the majority
of files this is the first line, except for scripts which require the
'#!PATH_TO_INTERPRETER' in the first line.  For those scripts the SPDX
identifier goes into the second line.

[1] https://www.kernel.org/doc/Documentation/process/license-rules.rst

Reviewed-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
Signed-off-by: Igor Opaniuk <igor.opaniuk@gmail.com>
Link: https://lore.kernel.org/r/20240209192045.3961832-3-igor.opaniuk@foundries.io
Signed-off-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
diff --git a/cmd/avb.c b/cmd/avb.c
index 783f51b..ce8b638 100644
--- a/cmd/avb.c
+++ b/cmd/avb.c
@@ -1,8 +1,6 @@
-
+// SPDX-License-Identifier: GPL-2.0+
 /*
  * (C) Copyright 2018, Linaro Limited
- *
- * SPDX-License-Identifier:	GPL-2.0+
  */
 
 #include <avb_verify.h>