drm/amdgpu:fix gfx fence allocate size

1, for sriov, we need 8dw for the gfx fence due to CP
behaviour
2, cleanup wrong logic in wptr/rptr wb alloc and free

Change-Id: Ifbfed17a4621dae57244942ffac7de1743de0294
Signed-off-by: Monk Liu <Monk.Liu@amd.com>
Signed-off-by: Xiangliang Yu <Xiangliang.Yu@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu.h b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
index ebd077f..51d1364 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu.h
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu.h
@@ -1192,7 +1192,9 @@ struct amdgpu_wb {
 int amdgpu_wb_get(struct amdgpu_device *adev, u32 *wb);
 void amdgpu_wb_free(struct amdgpu_device *adev, u32 wb);
 int amdgpu_wb_get_64bit(struct amdgpu_device *adev, u32 *wb);
+int amdgpu_wb_get_256Bit(struct amdgpu_device *adev, u32 *wb);
 void amdgpu_wb_free_64bit(struct amdgpu_device *adev, u32 wb);
+void amdgpu_wb_free_256bit(struct amdgpu_device *adev, u32 wb);
 
 void amdgpu_get_pcie_info(struct amdgpu_device *adev);