feat[mpp_dec]: Export raw decoder COLMV metadata

[Robolightning]

Summary

Add opt-in raw decoder COLMV export for RK3588 H.264/H.265 decode on the VDPU34x path.

The decoder config adds:

• base:enable_colmv — disabled by default
• KEY_DEC_COLMV — raw hardware COLMV MppBuffer
• KEY_DEC_COLMV_FMT — hardware layout identifier
• KEY_DEC_COLMV_SIZE — valid payload size for the current frame

The exported buffer is retained for the lifetime of the output MppFrame.

Semantics

This exposes the decoder's existing hardware-generated COLMV buffer. It is raw, hardware-specific data; this is not a portable or already-decoded motion-vector API.

When base:enable_colmv is disabled, the HAL export path is skipped and performs no COLMV metadata access, buffer copy, or cache synchronization.

When enabled:

• no COLMV payload copy is performed
• no implicit CPU cache synchronization is performed
• CPU consumers should use mpp_buffer_sync_ro_begin() / mpp_buffer_sync_ro_end() around reads
• DMA consumers can use the exported buffer without a CPU readback
• the buffer remains owned by the output frame; consumers that need it beyond the frame lifetime must retain their own reference

Initial format identifiers cover:

• VDPU34x H.264 compressed COLMV
• VDPU34x H.264 uncompressed COLMV
• VDPU34x H.265 compressed COLMV

The export is currently gated to RK3588.

mpi_dec_test can enable and inspect the path with mpi_dec_colmv=1.

Validation

Validated on OrangePi 5 / RK3588 using the exact Git tree:

14cd9c6c64ee07ec100e2020fd829d0923f03b63

with commit:

cbf19a9e70a41cda2e417318c14efa6703d1002e

Validation included:

• full Release build with WARNINGS_AS_ERRORS=ON
• mpp_info_test
• mpp_dec_cfg_test
• mpp_sys_cfg_test
• H.264 decode with COLMV disabled: 90 frames
• H.264 with COLMV enabled: 90/90 non-zero COLMV frames, 89 unique payload hashes
• H.265 decode with COLMV disabled: 90 frames
• H.265 with COLMV enabled: 90/90 non-zero COLMV frames, 90 unique payload hashes
• no new matching decoder/IOMMU kernel faults

The enabled validation path intentionally performs CPU cache sync and hashes the COLMV bytes to verify the hardware output; that diagnostic readback is not part of the normal disabled path.