[Intel-gfx] [PATCH] drm/i915: Fix a use after free, and unbalanced refcounting

[shuang.he at intel.com]

Tested-By: PRC QA PRTS (Patch Regression Test System Contact: shuang.he at intel.com)
Task id: 5771
-------------------------------------Summary-------------------------------------
Platform          Delta          drm-intel-nightly          Series Applied
PNV                                  281/281              281/281
ILK                                  313/313              313/313
SNB                                  309/309              309/309
IVB                                  382/382              382/382
BYT                                  296/296              296/296
HSW                 -1              426/426              425/426
BDW                 -1              318/318              317/318
-------------------------------------Detailed-------------------------------------
Platform  Test                                drm-intel-nightly          Series Applied
*HSW  igt_kms_flip_dpms-off-confusion      PASS(1)      TIMEOUT(1)
*BDW  igt_gem_gtt_hog      PASS(1)      DMESG_WARN(1)
Note: You need to pay more attention to line start with '*'