crypto: user - fix memory leak in crypto_reportstat

In crypto_reportstat, a new skb is created by nlmsg_new(). This skb is
leaked if crypto_reportstat_alg() fails. Required release for skb is
added.

Fixes: cac5818c25d0 ("crypto: user - Implement a generic crypto statistics")
Cc: <stable@vger.kernel.org>
Signed-off-by: Navid Emamdoost <navid.emamdoost@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
