drm/i915/psr: Force manual PSR exit in older gens

To do frontbuffer tracking we are depending on Display WA #0884 to
exit PSR when there is a frontbuffer modification but according to
user reports a write to CURSURFLIVE do not cause PSR to exit in older
gens so lets force a PSR exit.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=110799


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>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Tested-by: Thomas Rohwer <trohwer85@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190617195154.30292-1-jose.souza@intel.com