[CRYPTO] Don't check for NULL before kfree()

Checking a pointer for NULL before calling kfree() on it is redundant.
This patch removes such checks from crypto/

Signed-off-by: Jesper Juhl <juhl-lkml@dif.dk>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>