drm/amdgpu: enable the static csa when mcbp enabled

CSA is the Context Save Area for preemption.

Acked-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Jack Xiao <Jack.Xiao@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>