radeonsi: create a new context for transcode with multiple video engines

For CHIP_GFX1100, there are 2 VCN instances but using unified queue i.e. decode and encode will go to HW via same ring type. With AMDGPU kernel scheduler, since the trancode is sharing the same pipe context, so that the gpu scheduler assign the decode and encode into the same VCN engine. In order to use both engines with transcode case, the new pipe context will be created when the case being detected, with that the transcode can be load balanced with multiple VCN engines.

Signed-off-by: Leo Liu leo.liu@amd.com