crypto: gcm - Only access common skcipher fields on spawn

As skcipher spawns may be of the type lskcipher, only the common
fields may be accessed.  This was already the case but use the
correct helpers to make this more obvious.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/gcm.c

@@ -576,10 +576,10 @@ static int crypto_gcm_create_common(struct crypto_template *tmpl,
 				    const char *ctr_name,
 				    const char *ghash_name)
 {
+	struct skcipher_alg_common *ctr;
 	u32 mask;
 	struct aead_instance *inst;
 	struct gcm_instance_ctx *ctx;
-	struct skcipher_alg *ctr;
 	struct hash_alg_common *ghash;
 	int err;
 
@@ -607,13 +607,12 @@ static int crypto_gcm_create_common(struct crypto_template *tmpl,
 				   ctr_name, 0, mask);
 	if (err)
 		goto err_free_inst;
-	ctr = crypto_spawn_skcipher_alg(&ctx->ctr);
+	ctr = crypto_spawn_skcipher_alg_common(&ctx->ctr);
 
 	/* The skcipher algorithm must be CTR mode, using 16-byte blocks. */
 	err = -EINVAL;
 	if (strncmp(ctr->base.cra_name, "ctr(", 4) != 0 ||
-	    crypto_skcipher_alg_ivsize(ctr) != 16 ||
-	    ctr->base.cra_blocksize != 1)
+	    ctr->ivsize != 16 || ctr->base.cra_blocksize != 1)
 		goto err_free_inst;
 
 	err = -ENAMETOOLONG;
@@ -634,7 +633,7 @@ static int crypto_gcm_create_common(struct crypto_template *tmpl,
 				       ctr->base.cra_alignmask;
 	inst->alg.base.cra_ctxsize = sizeof(struct crypto_gcm_ctx);
 	inst->alg.ivsize = GCM_AES_IV_SIZE;
-	inst->alg.chunksize = crypto_skcipher_alg_chunksize(ctr);
+	inst->alg.chunksize = ctr->chunksize;
 	inst->alg.maxauthsize = 16;
 	inst->alg.init = crypto_gcm_init_tfm;
 	inst->alg.exit = crypto_gcm_exit_tfm;