tools: bpftool: fix error message (prog -> object)

Change an error message to work for any object being
pinned not just programs.

Fixes: 71bb428fe2 ("tools: bpf: add bpftool")
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

tools/bpf/bpftool/common.c

@@ -237,7 +237,7 @@ int do_pin_any(int argc, char **argv, int (*get_fd_by_id)(__u32))
 
 	fd = get_fd_by_id(id);
 	if (fd < 0) {
-		p_err("can't get prog by id (%u): %s", id, strerror(errno));
+		p_err("can't open object by id (%u): %s", id, strerror(errno));
 		return -1;
 	}