remoteproc: mtk_scp_ipi: Constify buffer passed to scp_ipi_send()

scp_ipi_send() 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-v3-1-4d7fd27f037f@oss.qualcomm.com
Signed-off-by: Bjorn Andersson <andersson@kernel.org>

Author: krzk

drivers/remoteproc/mtk_scp_ipi.c

@@ -156,7 +156,7 @@ EXPORT_SYMBOL_GPL(scp_ipi_unlock);
  *
  * Return: 0 if sending data successfully, -error on error.
  **/
-int scp_ipi_send(struct mtk_scp *scp, u32 id, void *buf, unsigned int len,
+int scp_ipi_send(struct mtk_scp *scp, u32 id, const void *buf, unsigned int len,
 		 unsigned int wait)
 {
 	struct mtk_share_obj __iomem *send_obj = scp->send_buf;

include/linux/remoteproc/mtk_scp.h

@@ -58,7 +58,7 @@ int scp_ipi_register(struct mtk_scp *scp, u32 id, scp_ipi_handler_t handler,
 		     void *priv);
 void scp_ipi_unregister(struct mtk_scp *scp, u32 id);
 
-int scp_ipi_send(struct mtk_scp *scp, u32 id, void *buf, unsigned int len,
+int scp_ipi_send(struct mtk_scp *scp, u32 id, const void *buf, unsigned int len,
 		 unsigned int wait);
 
 unsigned int scp_get_vdec_hw_capa(struct mtk_scp *scp);