drm: move read_domains and write_domain into i915

drm: move read_domains and write_domain into i915

i915 is the only driver using those fields in the drm_gem_object
structure, so they only waste memory for all other drivers.

Move the fields into drm_i915_gem_object instead and patch the i915 code
with the following sed commands:

sed -i "s/obj->base.read_domains/obj->read_domains/g" drivers/gpu/drm/i915/*.c drivers/gpu/drm/i915/*/*.c
sed -i "s/obj->base.write_domain/obj->write_domain/g" drivers/gpu/drm/i915/*.c drivers/gpu/drm/i915/*/*.c

Change is only compile tested.

v2: move fields around as suggested by Chris.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20180216124338.9087-1-christian.koenig@amd.com
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>