drm/i915/ips: Add i915_ips_false_color debugfs file

Similar to FBC let's expose an debugfs file to control
IPS false color. Enabling this provides an immediate visual
feedback on whether IPS is working or not.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230327133942.22063-2-ville.syrjala@linux.intel.com


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