drm: Rename crtc_idr as object_idr to KMS cleanups

This patch solves this TODO task:
 drm_mode_config.crtc_idr is misnamed, since it contains all KMS object.
 Should be renamed to drm_mode_config.object_idr.

Signed-off-by: Shayenne da Luz Moura <shayenneluzmoura@gmail.com>
[danvet: resolve conflict with addition of privobj_list.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20181213212957.vkitkyl5cj2qh7qr@smtp.gmail.com