Claude review: drm: renesas: rz-du: mipi_dsi: Fix return path on error

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

Patch Review

**Bug analysis**: In the original code, `dma_alloc_coherent()` was the last operation in `rzg2l_mipi_dsi_probe()`, placed after `mipi_dsi_host_register()`. On allocation failure it executed:
```c
return -ENOMEM;
```
This bypassed the error cleanup labels (`err_phy`, `err_pm_disable`), leaking the `pm_runtime_enable()` state and the registered MIPI DSI host.

**Fix correctness**:

The allocation is moved to before `platform_set_drvdata()` and `pm_runtime_enable()`:
```c
dsi->dcs_buf_virt = dmam_alloc_coherent(dsi->dev, RZG2L_DCS_BUF_SIZE,
                                        &dsi->dcs_buf_phys, GFP_KERNEL);
if (!dsi->dcs_buf_virt)
    return -ENOMEM;
```
At this point in the probe function, only `devm_*` managed resources have been acquired (clocks, resets, ioremap), so a plain `return` is safe — `devm` teardown handles everything. The switch from `dma_alloc_coherent` to `dmam_alloc_coherent` is the right choice: it's the device-managed variant, so the buffer is automatically freed when the device is unbound, eliminating the need for the explicit `dma_free_coherent()` in `remove()`.

**Remove path**: The `dma_free_coherent()` call is correctly removed from `rzg2l_mipi_dsi_remove()` since `dmam_alloc_coherent()` handles cleanup automatically.

**Device argument consistency**: The original code used `dsi->host.dev` as the device for `dma_alloc_coherent()` / `dma_free_coherent()`, while the new code uses `dsi->dev`. Looking at the probe function, `dsi->host.dev` is assigned to `dsi->dev` later in the function (line 1475: `dsi->host.dev = dsi->dev`), so using `dsi->dev` directly is correct and actually necessary since `dsi->host.dev` isn't set yet at the new call site.

**No issues found.** The patch is minimal, well-targeted, and correctly fixes both the immediate error-path bug and the broader resource management concern by using the managed API.

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Generated by Claude Code Patch Reviewer