crypto: user - Zeroize whole structure given to user space

For preventing uninitialized data to be given to user-space (and so leak
potential useful data), the crypto_stat structure must be correctly
initialized.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Fixes: cac5818c ("crypto: user - Implement a generic crypto statistics")
Signed-off-by: Corentin Labbe <clabbe@baylibre.com>
[EB: also fix it in crypto_reportstat_one()]
[EB: use sizeof(var) rather than sizeof(type)]
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>