[Intel-gfx] RFC: Add write flag to reservation object fences

[Christian König]

Hi everyone,

This set of patches tries to improve read after write hazard handling for reservation objects.

It allows us to specify for each shared fence if it represents a write operation.

Based on this the i915 driver is modified to always wait for all writes before pageflip and the previously used workaround is removed from amdgpu.

Please comment,
Christian.