Claude review: drm/loongson: use drm_gem_ttm_dumb_map_offset()

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

Patch Review

**Correctness:** The removed `lsdc_dumb_map_offset()` at `lsdc_gem.c:147-161` is functionally identical to `drm_gem_ttm_dumb_map_offset()` at `drm_gem_ttm_helper.c:137-151` — same object lookup, same `drm_vma_node_offset_addr()` call, same `drm_gem_object_put()`, same return values. This is a safe substitution.

**Changes are complete:**
- `lsdc_drv.c`: Adds `#include <drm/drm_gem_ttm_helper.h>` and swaps `.dumb_map_offset` assignment — correct.
- `lsdc_gem.c`: Removes the function body — correct.
- `lsdc_gem.h`: Removes the declaration — correct.
- No remaining references to `lsdc_dumb_map_offset` exist in the tree after this patch.

**Minor nit:** The removal in `lsdc_gem.c` leaves a double blank line (the original blank before the function plus the blank after the closing brace). This is cosmetically harmless but could be cleaned up to a single blank line. Very minor — not worth blocking.

**Other drivers using the same pattern:** Multiple TTM-based drivers (xe, nouveau, vmwgfx, qxl, hibmc) already use `drm_gem_ttm_dumb_map_offset()`, so this aligns loongson with established convention.

Reviewed-by: looks appropriate here.

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Generated by Claude Code Patch Reviewer