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>
diff --git a/crypto/xcbc.c b/crypto/xcbc.c
index 9265e00..598ec88 100644
--- a/crypto/xcbc.c
+++ b/crypto/xcbc.c
@@ -239,10 +239,12 @@ static int xcbc_create(struct crypto_template *tmpl, struct rtattr **tb)
 	inst->alg.final = crypto_xcbc_digest_final;
 	inst->alg.setkey = crypto_xcbc_digest_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;
 }
@@ -250,7 +252,6 @@ static int xcbc_create(struct crypto_template *tmpl, struct rtattr **tb)
 static struct crypto_template crypto_xcbc_tmpl = {
 	.name = "xcbc",
 	.create = xcbc_create,
-	.free = shash_free_instance,
 	.module = THIS_MODULE,
 };