drm/amdgpu: Don't set struct drm_driver.output_poll_changed

Don't set struct drm_driver.output_poll_changed. It's used to restore
the fbdev console. But as amdgpu uses generic fbdev emulation, the
console is being restored by the DRM client helpers already. See the
functions drm_kms_helper_hotplug_event() and
drm_kms_helper_connector_hotplug_event() in drm_probe_helper.c.

v2:
	* fix commit description (Christian)

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221103151446.2638-5-tzimmermann@suse.de