drm/i915/display: Enable PSR2 selective fetch by default

With all the past fixes now this feature is functional and can be
enabled by default in desktop enviroments that uses compositor.

Cc: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210930001409.254817-8-jose.souza@intel.com