crypto: n2 - remove null check before kfree

kfree on NULL pointer is a no-op and therefore checking it is redundant.

Signed-off-by: Himanshu Jha <himanshujha199640@gmail.com>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>