Revert "i915: Add GBM_BO_USE_HW_VIDEO_DECODER use flag"

This reverts commit 1bd7b04a.

Reason for revert: Breaks video decoding on most intel platforms, e.g., caroline and samus

Original change's description:
> i915: Add GBM_BO_USE_HW_VIDEO_DECODER use flag
> 
> This flag is used to indicate that the platform video decoder will be
> writing into this buffer and that it should be allocated
> accordingly. On Intel, this means that we have to allocate y-tiled
> NV12 for libva to be able to decode to the buffer.
> 
> We force gralloc NV12 allocations to be linear for now, since ARC++
> doesn't properly pass modifiers to ChromeOS.
> 
> BUG=822346
> TEST=test_that graphics_Gbm
> 
> Change-Id: I840c30d22355d26816df718b49717407e2e4620f
> Reviewed-on: https://chromium-review.googlesource.com/996648


> Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
> Tested-by: Kristian H. Kristensen <hoegsberg@chromium.org>
> Reviewed-by: Kristian H. Kristensen <hoegsberg@chromium.org>

Bug: 822346, 845076
Change-Id: I7681ddb66e4789951e840821993fc5562a55d1af
Reviewed-on: https://chromium-review.googlesource.com/1066032


Tested-by: Hirokazu Honda <hiroh@chromium.org>
Reviewed-by: Kuo Jen Wei <inker@chromium.org>
Reviewed-by: Tomasz Figa <tfiga@chromium.org>