crypto: s5p-sss - Remove useless check for non-null request

ahash_request 'req' argument passed by the caller
s5p_hash_handle_queue() cannot be NULL here because it is obtained from
non-NULL pointer via container_of().

This fixes smatch warning:
    drivers/crypto/s5p-sss.c:1213 s5p_hash_prepare_request() warn: variable dereferenced before check 'req' (see line 1208)

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>