cypto: mediatek - fix leaks in mtk_desc_ring_alloc

In the init loop, if an error occurs in function 'dma_alloc_coherent',
then goto the err_cleanup section, after run i--,
in the array ring, the struct mtk_ring with index i will not be released,
causing memory leaks

Fixes: 785e5c61 ("crypto: mediatek - Add crypto driver support for some MediaTek chips")
Cc: Ryder Lee <ryder.lee@mediatek.com>
Signed-off-by: Xiaoliang Pang <dawning.pang@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/mediatek/mtk-platform.c

@@ -469,13 +469,13 @@ static int mtk_desc_ring_alloc(struct mtk_cryp *cryp)
 	return 0;
 
 err_cleanup:
-	for (; i--; ) {
+	do {
 		dma_free_coherent(cryp->dev, MTK_DESC_RING_SZ,
 				  ring[i]->res_base, ring[i]->res_dma);
 		dma_free_coherent(cryp->dev, MTK_DESC_RING_SZ,
 				  ring[i]->cmd_base, ring[i]->cmd_dma);
 		kfree(ring[i]);
-	}
+	} while (i--);
 	return -ENOMEM;
 }