drm/shmem-helper: Put booleans in the end of struct drm_gem_shmem_object

Group all 1-bit boolean members of struct drm_gem_shmem_object in the end
of the structure, allowing compiler to pack data better and making code to
look more consistent.

Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Suggested-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Link: https://lore.kernel.org/all/20230108210445.3948344-5-dmitry.osipenko@collabora.com/