drm/i915/vrr: s/crtc_state/old_crtc_state/ in intel_vrr_transcoder_disable()

drm/i915/vrr: s/crtc_state/old_crtc_state/ in intel_vrr_transcoder_disable()

We generally use the 'old_crtc_state' in the disable functions to
make it clear these generally get called when the hardware is
still using the old crtc state rather than the new crtc state.
Rename the intel_vrr_transcoder_disable() 'crtc_state' parameter
to 'old_crtc_state' for consistency.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20251020185038.4272-19-ville.syrjala@linux.intel.com
Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>