drm/i915/rkl: Disable PSR2

RKL doesn't have PSR2 HW tracking, it was replaced by software/manual
tracking.  The driver is required to track the areas that needs update
and program hardware to send selective updates.

So until the software tracking is implemented, PSR2 needs to be disabled
for platforms without PSR2 HW tracking.

BSpec: 50422
BSpec: 50424

Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200603211529.3005059-15-matthew.d.roper@intel.com