Claude review: drm/mediatek: Convert legacy DRM logging to drm_* helpers in mtk_dsi.c

[Claude Code Review Bot <claude-review@example.com>]

Patch Review

**Commit message error:**

> This change aligns the radeon driver with the DRM TODO item

This should say "mediatek driver", not "radeon driver". Copy-paste error.

**Bug: Declaration after statement (build break)**

At `mtk_dsi_switch_to_cmd_mode()`, the new variable is declared after executable statements:

```c
static s32 mtk_dsi_switch_to_cmd_mode(struct mtk_dsi *dsi, u8 irq_flag, u32 t)
{
	mtk_dsi_irq_data_clear(dsi, irq_flag);
	mtk_dsi_set_cmd_mode(dsi);
	struct drm_device *drm = dsi->bridge.dev;  // <-- after statements
```

The declaration must be moved to the top of the function, before the two function calls. This will fail to compile with `-Wdeclaration-after-statement -Werror`.

**Bug: NULL `bridge.dev` in `mtk_dsi_host_attach()` (potential NULL deref)**

```c
static int mtk_dsi_host_attach(struct mipi_dsi_host *host,
			       struct mipi_dsi_device *device)
{
	struct mtk_dsi *dsi = host_to_dsi(host);
	struct device *dev = host->dev;
	struct drm_device *drm = dsi->bridge.dev;  // <-- NULL here
	...
	drm_bridge_add(&dsi->bridge);              // does NOT set bridge.dev

	ret = component_add(host->dev, &mtk_dsi_component_ops);
	if (ret) {
		drm_err(drm, ...);  // passes NULL drm_device
```

`bridge.dev` is set by `drm_bridge_attach()` (called inside `mtk_dsi_encoder_init()` which runs during `mtk_dsi_bind()`, triggered by the component framework *after* `component_add()`). At the point where `drm` is captured, it is NULL. The `drm_err(drm, ...)` call with a NULL first argument will crash. This call site should either keep using `DRM_ERROR()` or use `dev_err(host->dev, ...)` instead.

**Similarly suspect: `mtk_dsi_host_transfer()` and `mtk_dsi_wait_for_idle()`**

These functions also access `dsi->bridge.dev`. While `bridge.dev` is likely valid during normal runtime (the bridge should be attached by then), it's worth verifying that these code paths cannot be reached before the bridge is fully attached, or during teardown after `drm_bridge_detach()` has cleared `bridge.dev` to NULL.

**Minor: trailing `\n` in drm_* calls**

The `drm_*()` helpers already append a newline. The existing `DRM_*()` macros also append a newline, so the `\n` in the format strings was always redundant (producing double newlines). While this patch is just a mechanical conversion and isn't introducing the issue, it would be nice to clean up the trailing `\n` as part of this conversion.

**Correct conversions:**

The conversions in `mtk_dsi_config_vdo_timing_per_line_lp()`, `mtk_dsi_wait_for_irq_done()`, `mtk_dsi_bridge_atomic_pre_enable()`, and `mtk_dsi_encoder_init()` all look correct — `dsi->bridge.dev` or `bridge->dev` is valid in those contexts.

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