[CRYPTO]: crypto_free_tfm() callers no longer need to check for NULL

Since the patch to add a NULL short-circuit to crypto_free_tfm() went in,
there's no longer any need for callers of that function to check for NULL.
This patch removes the redundant NULL checks and also a few similar checks
for NULL before calls to kfree() that I ran into while doing the
crypto_free_tfm bits.

I've succesfuly compile tested this patch, and a kernel with the patch 
applied boots and runs just fine.

When I posted the patch to LKML (and other lists/people on Cc) it drew the
following comments :

 J. Bruce Fields commented
  "I've no problem with the auth_gss or nfsv4 bits.--b."

 Sridhar Samudrala said
  "sctp change looks fine."

 Herbert Xu signed off on the patch.

So, I guess this is ready to be dropped into -mm and eventually mainline.

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