[Intel-gfx] [PATCH] drm/atomic: Make sure lock is held in trylock contexts.

[shuang.he at intel.com]

Tested-By: Intel Graphics QA PRTS (Patch Regression Test System Contact: shuang.he at intel.com)
Task id: 7273
-------------------------------------Summary-------------------------------------
Platform          Delta          drm-intel-nightly          Series Applied
ILK                                  302/302              302/302
SNB                                  315/315              315/315
IVB                                  336/336              336/336
BYT                 -2              283/283              281/283
HSW                                  378/378              378/378
-------------------------------------Detailed-------------------------------------
Platform  Test                                drm-intel-nightly          Series Applied
*BYT  igt at gem_partial_pwrite_pread@reads-uncached      PASS(1)      FAIL(1)
*BYT  igt at gem_tiled_partial_pwrite_pread@reads      PASS(1)      FAIL(1)
Note: You need to pay more attention to line start with '*'