drm/i915/gvt: Add error handling for intel_gvt_scan_and_shadow_workload

When an error occurs after shadow_indirect_ctx, this patch is to do the
proper cleanup and rollback to the original states for shadowed indirect
context before the workload is abandoned.

v2:
- split the mixed several error paths for better review. (Zhenyu)

v3:
- no return check for clean up functions. (Changbin)

v4:
- expose and reuse the existing release_shadow_wa_ctx. (Zhenyu)

v5:
- move the release function to scheduler.c file. (Zhenyu)

v6:
- move error handling code of intel_gvt_scan_and_shadow_workload
  to here. (Zhenyu)

Signed-off-by: fred gao <fred.gao@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>