dmaengine: hisilicon: Annotate struct hisi_dma_dev with __counted_by

Prepare for the coming implementation by GCC and Clang of the __counted_by
attribute. Flexible array members annotated with __counted_by can have
their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
(for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).

As found with Coccinelle[1], add __counted_by for struct hisi_dma_dev.

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci

Cc: Vinod Koul <vkoul@kernel.org>
Cc: Zhou Wang <wangzhou1@hisilicon.com>
Cc: Jie Hai <haijie1@huawei.com>
Cc: dmaengine@vger.kernel.org
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Link: https://lore.kernel.org/r/20230817235859.49846-5-keescook@chromium.orgSigned-off-by: Vinod Koul <vkoul@kernel.org>

drivers/dma/hisi_dma.c

@@ -163,7 +163,7 @@ struct hisi_dma_dev {
 	u32 chan_depth;
 	enum hisi_dma_reg_layout reg_layout;
 	void __iomem *queue_base; /* queue region start of register */
-	struct hisi_dma_chan chan[];
+	struct hisi_dma_chan chan[] __counted_by(chan_num);
 };
 
 #ifdef CONFIG_DEBUG_FS