drm/i915/psr: Use WA to force HW tracking to exit PSR2

This WA also works fine for PSR2, triggering a selective update when
possible.

Acked-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181003205031.32474-4-jose.souza@intel.com