drm/amd/amdgpu: add Polaris12 support (v3)

v2: agd: squash in various fixes
v3: agd: squash in:
drm/amdgpu: remove unnecessary smc sk firmware for polaris12

Signed-off-by: Junwei Zhang <Jerry.Zhang@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Ken Wang  <Qingqing.Wang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/drivers/gpu/drm/amd/include/amd_shared.h b/drivers/gpu/drm/amd/include/amd_shared.h
index c02469a..5f59117 100644
--- a/drivers/gpu/drm/amd/include/amd_shared.h
+++ b/drivers/gpu/drm/amd/include/amd_shared.h
@@ -46,6 +46,7 @@ enum amd_asic_type {
 	CHIP_STONEY,
 	CHIP_POLARIS10,
 	CHIP_POLARIS11,
+	CHIP_POLARIS12,
 	CHIP_LAST,
 };