Revert "drm/nouveau/disp: Set drm_mode_config_funcs.atomic_(check|commit)"

Revert "drm/nouveau/disp: Set drm_mode_config_funcs.atomic_(check|commit)"

This reverts commit 604826acb3f53c6648a7ee99a3914ead680ab7fb.

Apparently there is more to supporting atomic modesetting than
providing atomic_(check|commit) callbacks. Before this revert:

WARNING: [] drivers/gpu/drm/drm_plane.c:389 at .__drm_universal_plane_init+0x13c/0x794 [drm], CPU#1: modprobe/1790
BUG: Kernel NULL pointer dereference on read at 0x00000000
.drm_atomic_get_plane_state+0xd4/0x210 [drm] (unreliable)
.drm_client_modeset_commit_atomic+0xf8/0x338 [drm]
.drm_client_modeset_commit_locked+0x80/0x260 [drm]
.drm_client_modeset_commit+0x40/0x7c [drm]
.__drm_fb_helper_restore_fbdev_mode_unlocked.part.0+0xfc/0x108 [drm_kms_helper]
.drm_fb_helper_set_par+0x8c/0xb8 [drm_kms_helper]
.fbcon_init+0x31c/0x618
[...]
.__drm_fb_helper_initial_config_and_unlock+0x474/0x7f4 [drm_kms_helper]
.drm_fbdev_client_hotplug+0xb0/0x120 [drm_client_lib]
.drm_client_register+0x88/0xe4 [drm]
.drm_fbdev_client_setup+0x12c/0x19b4 [drm_client_lib]
.drm_client_setup+0x15c/0x18c [drm_client_lib]
.nouveau_drm_probe+0x19c/0x268 [nouveau]

Fixes: 604826acb3f5 ("drm/nouveau/disp: Set drm_mode_config_funcs.atomic_(check|commit)")
Reported-by: John Ogness <john.ogness@linutronix.de>
Closes: https://lore.kernel.org/lkml/87ldhf1prw.fsf@jogness.linutronix.de
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Tested-by: Daniel Palmer <daniel@thingy.jp>
Link: https://patch.msgid.link/20260130113230.2311221-1-john.ogness@linutronix.de
Signed-off-by: Danilo Krummrich <dakr@kernel.org>