Fix encoder->possible_clones and validate correctness of possible_clones value

Summary

In the Linux kernel, the following vulnerability has been resolved: drm/radeon: Fix encoder->possible_clones Include the encoder itself in its possible_clones bitmask. In the past nothing validated that drivers were populating possible_clones correctly, but that changed in commit 74d2aacbe840 ("drm: Validate encoder->possible_clones"). Looks like radeon never got the memo and is still not following the rules 100% correctly. This results in some warnings during driver initialization: Bogus possible_clones: [ENCODER:46:TV-46] possible_clones=0x4 (full encoder mask=0x7) WARNING: CPU: 0 PID: 170 at drivers/gpu/drm/drm_mode_config.c:615 drm_mode_config_validate+0x113/0x39c ... (cherry picked from commit 3b6e7d40649c0d75572039aff9d0911864c689db)