drm/i915/ips: Make IPS debugfs per-crtc

IPS is a per-pipe feature, so let's move the debugfs stuff
under the crtc directory, and only register it when IPS
is actually available.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230327133942.22063-1-ville.syrjala@linux.intel.com


Reviewed-by: Jani Nikula <jani.nikula@intel.com>