The intention is that we first try to pin the current vma into the
mappable aperture only if it is already in use or it fits in the free
space and will not cause contention. The first attempt was meant to be
using PIN_NOEVICT to reuse the current vma if possible, following up
with different eviction strategies.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=111485
Fixes: 6846895f ("drm/i915: Replace PIN_NONFAULT with calls to PIN_NOEVICT")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Matthew Auld <matthew.auld@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190826130750.17272-1-chris@chris-wilson.co.uk