crypto: Use ERR_CAST

Use ERR_CAST(x) rather than ERR_PTR(PTR_ERR(x)).  The former makes more
clear what is the purpose of the operation, which otherwise looks like a
no-op.

The semantic patch that makes this change is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@@
type T;
T x;
identifier f;
@@

T f (...) { <+...
- ERR_PTR(PTR_ERR(x))
+ x
 ...+> }

@@
expression x;
@@

- ERR_PTR(PTR_ERR(x))
+ ERR_CAST(x)
// </smpl>

Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/authenc.c

@@ -616,7 +616,7 @@ static struct crypto_instance *crypto_authenc_alloc(struct rtattr **tb)
 	auth = ahash_attr_alg(tb[1], CRYPTO_ALG_TYPE_HASH,
 			       CRYPTO_ALG_TYPE_AHASH_MASK);
 	if (IS_ERR(auth))
-		return ERR_PTR(PTR_ERR(auth));
+		return ERR_CAST(auth);
 
 	auth_base = &auth->base;