[Intel-gfx] [PATCH] drm/i915: Keep ring->active_list and ring->requests_list consistent

[shuang.he at intel.com]

Tested-By: PRC QA PRTS (Patch Regression Test System Contact: shuang.he at intel.com)
Task id: 5996
-------------------------------------Summary-------------------------------------
Platform          Delta          drm-intel-nightly          Series Applied
PNV                                  272/272              272/272
ILK                                  301/301              301/301
SNB                                  303/303              303/303
IVB                                  342/342              342/342
BYT                                  287/287              287/287
HSW                                  362/362              362/362
BDW                                  308/308              308/308
-------------------------------------Detailed-------------------------------------
Platform  Test                                drm-intel-nightly          Series Applied
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