[Intel-gfx] [PATCH 2/2] drm/i915: Also call frontbuffer flip when disabling planes.

[shuang.he at intel.com]

Tested-By: Intel Graphics QA PRTS (Patch Regression Test System Contact: shuang.he at intel.com)
Task id: 6860
-------------------------------------Summary-------------------------------------
Platform          Delta          drm-intel-nightly          Series Applied
ILK                 -1              296/296              295/296
SNB                                  316/316              316/316
IVB                                  342/342              342/342
BYT                 -1              286/286              285/286
HSW                                  378/378              378/378
-------------------------------------Detailed-------------------------------------
Platform  Test                                drm-intel-nightly          Series Applied
*ILK  igt at kms_flip@flip-vs-rmfb-interruptible      PASS(1)      DMESG_WARN(1)
*BYT  igt at gem_partial_pwrite_pread@reads-display      PASS(1)      FAIL(1)
Note: You need to pay more attention to line start with '*'