remoteproc: mtk_scp: Constify buffer passed to scp_send_ipi()

scp_send_ipi() should only send the passed buffer, without modifying its
contents, so mark pointer 'buf' as pointer to const.

Acked-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20260317-rpmsg-send-const-v3-2-4d7fd27f037f@oss.qualcomm.com
Signed-off-by: Bjorn Andersson <andersson@kernel.org>

Author: krzk

drivers/remoteproc/mtk_scp.c

@@ -1078,7 +1078,7 @@ static void scp_unregister_ipi(struct platform_device *pdev, u32 id)
 	scp_ipi_unregister(scp, id);
 }
 
-static int scp_send_ipi(struct platform_device *pdev, u32 id, void *buf,
+static int scp_send_ipi(struct platform_device *pdev, u32 id, const void *buf,
 			unsigned int len, unsigned int wait)
 {
 	struct mtk_scp *scp = platform_get_drvdata(pdev);

include/linux/rpmsg/mtk_rpmsg.h

@@ -25,7 +25,7 @@ struct mtk_rpmsg_info {
 			    ipi_handler_t handler, void *priv);
 	void (*unregister_ipi)(struct platform_device *pdev, u32 id);
 	int (*send_ipi)(struct platform_device *pdev, u32 id,
-			void *buf, unsigned int len, unsigned int wait);
+			const void *buf, unsigned int len, unsigned int wait);
 	int ns_ipi_id;
 };