libbpf: Correct debug message in btf__load_vmlinux_btf

In the function btf__load_vmlinux_btf, the debug message incorrectly
refers to 'path' instead of 'sysfs_btf_path'.

Signed-off-by: Chen Shen <peterchenshen@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/bpf/20240302062218.3587-1-peterchenshen@gmail.com

Author: ShenChen1

tools/lib/bpf/btf.c

@@ -4968,7 +4968,7 @@ struct btf *btf__load_vmlinux_btf(void)
 			pr_warn("failed to read kernel BTF from '%s': %d\n", sysfs_btf_path, err);
 			return libbpf_err_ptr(err);
 		}
-		pr_debug("loaded kernel BTF from '%s'\n", path);
+		pr_debug("loaded kernel BTF from '%s'\n", sysfs_btf_path);
 		return btf;
 	}