Xpout and Xqout checked in wrong fashion

In the starting of the module ossl_rsa_fips186_4_gen_prob_primes, local variables are assigned as NULL i.e.

BIGNUM *Xpout = NULL, *Xqout = NULL;

while assigning to Xpo and Xqo they have been checked if they are NULL or not which is of no USE as they are already assigned with NULL.

Removed that check.

CLA: trivial