[Intel-gfx] [PATCH] drm/i915: Disable execlists by default for gen8

[shuang.he at intel.com]

Tested-By: Intel Graphics QA PRTS (Patch Regression Test System Contact: shuang.he at intel.com)
Task id: 6182
-------------------------------------Summary-------------------------------------
Platform          Delta          drm-intel-nightly          Series Applied
PNV                 -4              276/276              272/276
ILK                                  301/301              301/301
SNB                                  316/316              316/316
IVB                 -2              328/328              326/328
BYT                                  285/285              285/285
HSW                                  394/394              394/394
BDW                 -6              321/321              315/321
-------------------------------------Detailed-------------------------------------
Platform  Test                                drm-intel-nightly          Series Applied
 PNV  igt at gen3_render_linear_blits      FAIL(4)PASS(5)      FAIL(1)PASS(1)
 PNV  igt at gen3_render_mixed_blits      FAIL(5)PASS(4)      FAIL(2)
 PNV  igt at gen3_render_tiledx_blits      FAIL(5)PASS(5)      FAIL(2)
 PNV  igt at gen3_render_tiledy_blits      FAIL(4)PASS(5)      FAIL(1)PASS(1)
 IVB  igt at gem_pwrite_pread@uncached-copy-performance      DMESG_WARN(1)PASS(4)      DMESG_WARN(2)
(dmesg patch applied)drm:i915_hangcheck_elapsed[i915]]*ERROR*Hangcheck_timer_elapsed...blitter_ring_idle at Hangcheck timer elapsed... blitter ring idle
*IVB  igt at gem_storedw_batches_loop@normal      PASS(2)      DMESG_WARN(1)PASS(1)
(dmesg patch applied)drm:i915_hangcheck_elapsed[i915]]*ERROR*Hangcheck_timer_elapsed...blitter_ring_idle at Hangcheck timer elapsed... blitter ring idle
*BDW  igt at gem_evict_everything@forked-interruptible      PASS(2)      TIMEOUT(2)
*BDW  igt at gem_evict_everything@forked-normal      PASS(2)      TIMEOUT(2)
*BDW  igt at gem_ringfill@render      PASS(2)      TIMEOUT(1)
*BDW  igt at gem_ringfill@render-interruptible      PASS(2)      TIMEOUT(1)
*BDW  igt at gem_ring_sync_copy@sync-render-blitter-read-write      PASS(2)      FAIL(1)
*BDW  igt at gem_ring_sync_copy@sync-render-blitter-write-read      PASS(2)      FAIL(1)
Note: You need to pay more attention to line start with '*'