drm/amdgpu/jpeg2.6: Add jpeg2.6 support

Aldebaran is using jpeg2.6, and the main change is jpeg2.6 using
AMDGPU_MMHUB_0, and jpeg2.5 using AMDGPU_MMHUB_1.

Signed-off-by: James Zhu <James.Zhu@amd.com>
Reviewed-by: Leo Liu <leo.liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>