crypto: nx - Fix memcpy() over-reading in nonce

Fix typo in memcpy() where size should be CTR_RFC3686_NONCE_SIZE.

Fixes: 030f4e96 ("crypto: nx - Fix reentrancy bugs")
Cc: stable@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>