drm/amdgpu: pipeline evictions as well

This boosts Xonotic from 38fps to 47fps when artificially limiting VRAM to
256MB for testing. It should improve all CPU bound rendering situations
where we have a lot of swapping to/from VRAM.

Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>