drm/{i915, xe}: Suspend/resume fbdev emulation via client interfaces

drm/{i915, xe}: Suspend/resume fbdev emulation via client interfaces

Implement drm_client_dev_suspend() and drm_client_dev_resume() for
i915's fbdev emulation and call the helper via DRM client interfaces.
This is required to convert i915 and xe to DRM's generic fbdev client.
No functional changes.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241212170913.185939-2-tzimmermann@suse.de
Signed-off-by: Maarten Lankhorst <dev@lankhorst.se>