crypto: qat - fix mutex ordering in adf_rl

If the function validate_user_input() returns an error, the error path
attempts to unlock an unacquired mutex.
Acquire the mutex before calling validate_user_input(). This is not
strictly necessary but simplifies the code.

Fixes: d9fb8408

 ("crypto: qat - add rate limiting feature to qat_4xxx")
Signed-off-by: Damian Muszynski <damian.muszynski@intel.com>
Reviewed-by: Giovanni Cabiddu <giovanni.cabiddu@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>