Claude review: drm/v3d: Refactor CPU ioctl into unified submission chain

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

Patch Review

Merges the indirect CSD path into a single `struct v3d_submit`. The two-pass fence attachment is eliminated.

There's a subtlety worth noting: `v3d_lookup_bos()` is called *before* `v3d_setup_csd_jobs_and_bos()`, and the comment explains why:
```c
/* Look up the CPU jobs' BOs first, so v3d_setup_csd_jobs_and_bos(), which
 * locks all jobs' BOs at its end, picks them up too in the case of indirect
 * CSD.
 */
```
This ordering dependency is correct — `v3d_setup_csd_jobs_and_bos()` calls `v3d_submit_lock_reservations()` internally, which iterates all jobs' BOs.

**Observation**: After this patch, the `v3d_indirect_csd_info` struct still has `struct v3d_csd_job *job` and `struct drm_gem_object *indirect` members. The `job` pointer is set via `container_of(submit.jobs[1], ...)`. This cross-reference between the submit array and the indirect_csd struct is fine since both are stack-local and have the same lifetime.

No issues.

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