crypto: cryptd - make cryptd_max_cpu_qlen module parameter static

The cryptd_max_cpu_qlen module parameter is local to the source and does
not need to be in global scope, so make it static.

Cleans up sparse warning:
crypto/cryptd.c:35:14: warning: symbol 'cryptd_max_cpu_qlen' was not
declared. Should it be static?

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>