[Intel-gfx] [PATCH 4/4] drm/i915: use current mode if the size

[shuang.he at intel.com]

Tested-By: PRC QA PRTS (Patch Regression Test System Contact: shuang.he at intel.com)
-------------------------------------Summary-------------------------------------
Platform: baseline_drm_intel_nightly_pass_rate->patch_applied_pass_rate
BYT: pass/total=271/271->271/271
PNV: pass/total=269/271->269/271
ILK: pass/total=269/271->271/271
IVB: pass/total=271/271->271/271
SNB: pass/total=271/271->271/271
HSW: pass/total=271/271->271/271
BDW: pass/total=272/273->271/273
-------------------------------------Detailed-------------------------------------
test_platform: test_suite, test_case, result_with_drm_intel_nightly->result_with_patch_applied
ILK: Intel_gpu_tools, igt_kms_pipe_crc_basic_bad-nb-words-3, DMESG_WARN->PASS
ILK: Intel_gpu_tools, igt_kms_setmode_invalid-clone-single-crtc, DMESG_WARN->PASS
BDW: Intel_gpu_tools, igt_drv_missed_irq_hang, DMESG_WARN->PASS
BDW: Intel_gpu_tools, igt_gem_concurrent_blit_gtt-bcs-gpu-read-after-write-forked, PASS->TIMEOUT
BDW: Intel_gpu_tools, igt_gem_concurrent_blit_gttX-bcs-gpu-read-after-write-forked, PASS->TIMEOUT