drm/colorop: Fix blob property reference tracking in state lifecycle

In the Linux kernel, the following vulnerability has been resolved:

drm/colorop: Fix blob property reference tracking in state lifecycle

The colorop state blob property handling had memory leaks during state
duplication, destruction, and reset operations. The implementation
failed to follow the established pattern from drm_crtc's handling of
DEGAMMA/GAMMA blob properties.

Issues fixed:
- drm_colorop_atomic_destroy_state() was freeing state memory without
releasing the blob reference, causing a leak
- drm_colorop_reset() was directly freeing old state with kfree()
instead of properly destroying it, leaking blob references
- drm_colorop_cleanup() had duplicate blob cleanup code

Changes:
- Add __drm_atomic_helper_colorop_destroy_state() helper to properly
release blob references before freeing state memory
- Update drm_colorop_atomic_destroy_state() to call the helper
- Fix drm_colorop_reset() to use drm_colorop_atomic_destroy_state()
for proper cleanup of old state
- Simplify drm_colorop_cleanup() to use the common destruction path

This matches the well-tested pattern used by drm_crtc since 2016 and
ensures proper reference counting throughout the state lifecycle.

Co-developed by Claude Sonnet 4.5.