ASoC: SOF: mediatek: Constify struct mtk_adsp_ipc_ops

'struct mtk_adsp_ipc_ops' is not modified in these drivers.

Constifying this structure moves some data to a read-only section, so
increase overall security.

In order to do it, "struct mtk_adsp_ipc" also needs to be adjusted to this
new const qualifier.

On a x86_64, with allmodconfig:
Before:
======
   text	   data	    bss	    dec	    hex	filename
  15533	   2383	      0	  17916	   45fc	sound/soc/sof/mediatek/mt8195/mt8195.o

After:
=====
   text	   data	    bss	    dec	    hex	filename
  15557	   2367	      0	  17924	   4604	sound/soc/sof/mediatek/mt8195/mt8195.o
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Link: https://msgid.link/r/a45d6b2b5ec040ea0fc78fca662c2dca3f13a49f.1718312321.git.christophe.jaillet@wanadoo.frSigned-off-by: Mark Brown <broonie@kernel.org>

include/linux/firmware/mediatek/mtk-adsp-ipc.h

@@ -40,7 +40,7 @@ struct mtk_adsp_chan {
 struct mtk_adsp_ipc {
 	struct mtk_adsp_chan chans[MTK_ADSP_MBOX_NUM];
 	struct device *dev;
-	struct mtk_adsp_ipc_ops *ops;
+	const struct mtk_adsp_ipc_ops *ops;
 	void *private_data;
 };
 

sound/soc/sof/mediatek/mt8186/mt8186.c

@@ -82,7 +82,7 @@ static void mt8186_dsp_handle_request(struct mtk_adsp_ipc *ipc)
 	}
 }
 
-static struct mtk_adsp_ipc_ops dsp_ops = {
+static const struct mtk_adsp_ipc_ops dsp_ops = {
 	.handle_reply		= mt8186_dsp_handle_reply,
 	.handle_request		= mt8186_dsp_handle_request,
 };

sound/soc/sof/mediatek/mt8195/mt8195.c

@@ -82,7 +82,7 @@ static void mt8195_dsp_handle_request(struct mtk_adsp_ipc *ipc)
 	}
 }
 
-static struct mtk_adsp_ipc_ops dsp_ops = {
+static const struct mtk_adsp_ipc_ops dsp_ops = {
 	.handle_reply		= mt8195_dsp_handle_reply,
 	.handle_request		= mt8195_dsp_handle_request,
 };