drm/i915/display: Drop PSR support from HSW and BDW

At this point is sure that HSW and BDW will never have PSR enabled by
default, so here dropping it from device info and cleaning up code.

v2:
- enable psr support for display 9

Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: 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/20210827174253.51122-1-jose.souza@intel.com