get_user_pages_fast() can return zero in certain error paths. We should
handle that or else it means we accidentally return ERR_PTR(0) which is
NULL instead of an error pointer. The callers are not expecting that
and will crash with a NULL dereference.
Fixes: 033ddf12bcf5 ("tee: add register user memory") Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>