apparmor: Fix memleak in aa_simple_write_to_buffer()

When copy_from_user failed, the memory is freed by kvfree. however the
management struct and data blob are allocated independently, so only
kvfree(data) cause a memleak issue here. Use aa_put_loaddata(data) to
fix this issue.

Fixes: a6a52579 ("apparmor: split load data into management struct and data blob")
Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: John Johansen <john.johansen@canonical.com>