crypto: shash - convert shash_free_instance() to new style

Convert shash_free_instance() and its users to the new way of freeing
instances, where a ->free() method is installed to the instance struct
itself.  This replaces the weakly-typed method crypto_template::free().

This will allow removing support for the old way of freeing instances.

Also give shash_free_instance() a more descriptive name to reflect that
it's only for instances with a single spawn, not for any instance.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/vmac.c

@@ -660,10 +660,12 @@ static int vmac_create(struct crypto_template *tmpl, struct rtattr **tb)
 	inst->alg.final = vmac_final;
 	inst->alg.setkey = vmac_setkey;
 
+	inst->free = shash_free_singlespawn_instance;
+
 	err = shash_register_instance(tmpl, inst);
 	if (err) {
 err_free_inst:
-		shash_free_instance(shash_crypto_instance(inst));
+		shash_free_singlespawn_instance(inst);
 	}
 	return err;
 }
@@ -671,7 +673,6 @@ err_free_inst:
 static struct crypto_template vmac64_tmpl = {
 	.name = "vmac64",
 	.create = vmac_create,
-	.free = shash_free_instance,
 	.module = THIS_MODULE,
 };