drm: sti: use late_register and early_unregister callbacks

Make sti driver use register callback to move debugfs
initialization out of sub-components creation.
This will allow to convert driver .load() to
drm_dev_alloc() and drm_dev_register().

sti_compositor bring up 2 crtc but only one debugfs init is
needed so use drm_crtc_index to do it on the first one.
This can't be done in sti_drv because only sti_compositor have
access to the devices.
It is almost the same for sti_encoder which handle multiple
encoder while one only debugfs entry is needed so add a boolean
to avoid multiple debugfs initialization

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1466514580-15194-3-git-send-email-benjamin.gaignard@linaro.org

drivers/gpu/drm/sti/sti_mixer.c

@@ -181,7 +181,7 @@ static struct drm_info_list mixer1_debugfs_files[] = {
 	{ "mixer_aux", mixer_dbg_show, 0, NULL },
 };
 
-static int mixer_debugfs_init(struct sti_mixer *mixer, struct drm_minor *minor)
+int sti_mixer_debugfs_init(struct sti_mixer *mixer, struct drm_minor *minor)
 {
 	unsigned int i;
 	struct drm_info_list *mixer_debugfs_files;
@@ -393,8 +393,5 @@ struct sti_mixer *sti_mixer_create(struct device *dev,
 	DRM_DEBUG_DRIVER("%s created. Regs=%p\n",
 			 sti_mixer_to_str(mixer), mixer->regs);
 
-	if (mixer_debugfs_init(mixer, drm_dev->primary))
-		DRM_ERROR("MIXER debugfs setup failed\n");
-
 	return mixer;
 }