d3d12: Initialize d3d12_video_encoder_bitstream member m_uiOffset.
Fix defect reported by Coverity Scan.
Uninitialized scalar field (UNINIT_CTOR) uninit_member: Non-static class member m_uiOffset is not initialized in this constructor nor in any functions that it calls.
Fixes: b171a6ba ("d3d12: Add video encode implementation of pipe_video_codec") Signed-off-by: Vinson Lee vlee@freedesktop.org