drm/atomic: WARN about invalid drm_foo_get_state() usage

drm/atomic: WARN about invalid drm_foo_get_state() usage

drm_{crtc,plane,connector,private_obj}_get_state() must not
be called after the atomic check phase. At that point the commit
has been carved in stone and no new objects must be introduced
into it. WARN if anyone attempts to violate this rule.

Cc: Maxime Ripard <mripard@kernel.org>
Cc: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patch.msgid.link/20251017163327.9074-2-ville.syrjala@linux.intel.com
Reviewed-by: Maxime Ripard <mripard@kernel.org>