drm/i915/display: convert I915_STATE_WARN() to struct intel_display

drm/i915/display: convert I915_STATE_WARN() to struct intel_display

Convert I915_STATE_WARN() to struct intel_display *, and rename to
INTEL_DISPLAY_STATE_WARN(). Do some minor opportunistic struct
drm_i915_private to struct intel_display conversions while at it.

v2: crtc_state may be NULL in intel_connector_verify_state()

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241024162510.2410128-1-jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>