bpftool: Declare generator name

Most code generators declare its name so did this for bfptool.
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220509090247.5457-1-jasowang@redhat.com

tools/bpf/bpftool/gen.c

@@ -999,7 +999,7 @@ static int do_skeleton(int argc, char **argv)
 		codegen("\
 		\n\
 		/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */   \n\
-		/* THIS FILE IS AUTOGENERATED! */			    \n\
+		/* THIS FILE IS AUTOGENERATED BY BPFTOOL! */		    \n\
 		#ifndef %2$s						    \n\
 		#define %2$s						    \n\
 									    \n\
@@ -1015,7 +1015,7 @@ static int do_skeleton(int argc, char **argv)
 		\n\
 		/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */   \n\
 									    \n\
-		/* THIS FILE IS AUTOGENERATED! */			    \n\
+		/* THIS FILE IS AUTOGENERATED BY BPFTOOL! */		    \n\
 		#ifndef %2$s						    \n\
 		#define %2$s						    \n\
 									    \n\