bpf: Replace kvfree with kfree for kzalloc memory

These pointers are allocated by kzalloc. Therefore, replace kvfree() with
kfree() to avoid unnecessary is_vmalloc_addr() check in kvfree(). This is
the remaining unmodified part from [1].

Signed-off-by: Feng Yang <yangfeng@kylinos.cn>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20250811123949.552885-1-rongqianfeng@vivo.com [1]
Link: https://lore.kernel.org/bpf/20250827032812.498216-1-yangfeng59949@163.com