media: mtk-mdp: constify vb2_ops structure

Check for vb2_ops structures that are only stored in the ops field of a
vb2_queue structure. That field is declared const, so vb2_ops structures
that have this property can be declared as const also.

This issue was detected using Coccinelle and the following semantic patch:

@r disable optional_qualifier@
identifier i;
position p;
@@
static struct vb2_ops i@p = { ... };

@ok@
identifier r.i;
struct vb2_queue e;
position p;
@@
e.ops = &i@p;

@bad@
position p != {r.p,ok.p};
identifier r.i;
struct vb2_ops e;
@@
e@i@p

@depends on !bad disable optional_qualifier@
identifier r.i;
@@
static
+const
struct vb2_ops i = { ... };

Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/platform/mtk-mdp/mtk_mdp_m2m.c

@@ -621,7 +621,7 @@ static void mtk_mdp_m2m_buf_queue(struct vb2_buffer *vb)
 	v4l2_m2m_buf_queue(ctx->m2m_ctx, to_vb2_v4l2_buffer(vb));
 }
 
-static struct vb2_ops mtk_mdp_m2m_qops = {
+static const struct vb2_ops mtk_mdp_m2m_qops = {
 	.queue_setup	 = mtk_mdp_m2m_queue_setup,
 	.buf_prepare	 = mtk_mdp_m2m_buf_prepare,
 	.buf_queue	 = mtk_mdp_m2m_buf_queue,