drm/amdgpu/gfx10: add gfx config for navi12

got from mmCP_MAX_CONTEXT and mmPA_SC_FIFO_SIZE

v2: squash all navi asics together because the
settings are the same.

Signed-off-by: Xiaojie Yuan <xiaojie.yuan@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>