crypto: caam - Use struct_size()

Use struct_size() instead of hand-writing it, when allocating a structure
with a flex array.

This is less verbose, more robust and more informative.
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Gaurav Jain <gaurav.jain@nxp.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/caam/caamhash.c

@@ -708,9 +708,8 @@ static struct ahash_edesc *ahash_edesc_alloc(struct ahash_request *req,
 	gfp_t flags = (req->base.flags & CRYPTO_TFM_REQ_MAY_SLEEP) ?
 		       GFP_KERNEL : GFP_ATOMIC;
 	struct ahash_edesc *edesc;
-	unsigned int sg_size = sg_num * sizeof(struct sec4_sg_entry);
 
-	edesc = kzalloc(sizeof(*edesc) + sg_size, flags);
+	edesc = kzalloc(struct_size(edesc, sec4_sg, sg_num), flags);
 	if (!edesc) {
 		dev_err(ctx->jrdev, "could not allocate extended descriptor\n");
 		return NULL;