crypto: dh - comply with crypto_kpp_maxsize()

crypto_kpp_maxsize() asks for the output buffer size without
caring for errors. It allways assume that will be called after
a valid setkey. Comply with it and return what he wants.
Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/dh.c

@@ -147,7 +147,7 @@ static int dh_compute_value(struct kpp_request *req)
 	return ret;
 }
 
-static int dh_max_size(struct crypto_kpp *tfm)
+static unsigned int dh_max_size(struct crypto_kpp *tfm)
 {
 	struct dh_ctx *ctx = dh_get_ctx(tfm);