[Intel-gfx] [PATCH] drm/i915: Check obj->vma_list under the struct_mutex

[shuang.he at intel.com]

Tested-By: PRC QA PRTS (Patch Regression Test System Contact: shuang.he at intel.com)
Task id: 5765
-------------------------------------Summary-------------------------------------
Platform          Delta          drm-intel-nightly          Series Applied
PNV                 -1              282/282              281/282
ILK                                  313/313              313/313
SNB                                  309/323              309/323
IVB                                  380/380              380/380
BYT                                  296/296              296/296
HSW                 -1              425/425              424/425
BDW                 -1              318/318              317/318
-------------------------------------Detailed-------------------------------------
Platform  Test                                drm-intel-nightly          Series Applied
*PNV  igt_gen3_render_linear_blits      PASS(5)      CRASH(1)
*HSW  igt_gem_storedw_loop_blt      PASS(3)      DMESG_WARN(1)
*BDW  igt_gem_gtt_hog      PASS(8)      DMESG_WARN(1)
Note: You need to pay more attention to line start with '*'