bpftool: Fix -Wcast-qual warning

This cast was made by purpose for older libbpf where the
bpf_object_skeleton field is void * instead of const void *
to eliminate a warning (as i understand
-Wincompatible-pointer-types-discards-qualifiers) but this
cast introduces another warning (-Wcast-qual) for libbpf
where data field is const void *

It makes sense for bpftool to be in sync with libbpf from
kernel sources

Signed-off-by: Denys Zagorui <[email protected]>
Signed-off-by: Andrii Nakryiko <[email protected]>
Acked-by: Quentin Monnet <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]

src/gen.c

@@ -1209,7 +1209,7 @@ static int do_skeleton(int argc, char **argv)
 	codegen("\
 		\n\
 									    \n\
-			s->data = (void *)%2$s__elf_bytes(&s->data_sz);	    \n\
+			s->data = %2$s__elf_bytes(&s->data_sz);		    \n\
 									    \n\
 			obj->skeleton = s;				    \n\
 			return 0;					    \n\