d3d12: Initialize d3d12_video_encoder_references_manager_hevc::m_current_frame_idx.

Fix defect reported by Coverity Scan.

Uninitialized scalar field (UNINIT_CTOR)
uninit_member: Non-static class member m_current_frame_idx is not
initialized in this constructor nor in any functions that it calls.

Fixes: da11684e9db ("d3d12: Add HEVC Decode/Encode")
Signed-off-by: Vinson Lee <vlee@freedesktop.org>
Reviewed-by: Sil Vilerino <sivileri@microsoft.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/18654>
1 file changed