drm/i915/gvt: Factor out scan and shadow from workload dispatch

To perform the workload scan and shadow in ELSP writing stage for
performance consideration, the workload scan and shadow stuffs
should be factored out from dispatch_workload().

v2:Put context pin before i915_add_request;
   Refine the comments;
   Rename some APIs;

v3:workload->status should set only when error happens.
v4:i915_add_request is must to have after i915_gem_request_alloc.

Signed-off-by: Ping Gao <ping.a.gao@intel.com>
Reviewed-by: Zhi Wang <zhi.a.wang@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>

drivers/gpu/drm/i915/gvt/gvt.h

@@ -470,6 +470,8 @@ int intel_vgpu_init_opregion(struct intel_vgpu *vgpu, u32 gpa);
 int intel_vgpu_emulate_opregion_request(struct intel_vgpu *vgpu, u32 swsci);
 void populate_pvinfo_page(struct intel_vgpu *vgpu);
 
+int intel_gvt_scan_and_shadow_workload(struct intel_vgpu_workload *workload);
+
 struct intel_gvt_ops {
 	int (*emulate_cfg_read)(struct intel_vgpu *, unsigned int, void *,
 				unsigned int);