drm/i915/skl: Fix rc6 based gpu/system hang

drm/i915/skl: Fix rc6 based gpu/system hang

For all gt3 and gt4 skylake variants, extend the usage of
WaRsDisableCoarsePowerGating for all revisions. Without this
gt3 and gt4 skylakes up to atleast rev 0xa can gpu hang or
system hang.

Cc: Abdiel Janulgue <abdiel.janulgue@linux.intel.com>
Cc: Ben Widawsky <benjamin.widawsky@intel.com>
Cc: Timo Aaltonen <tjaalton@ubuntu.com>
Cc: <stable@vger.kernel.org>
Reported-by: Mikael Djurfeldt <mikael@djurfeldt.com>
References: https://bugs.freedesktop.org/show_bug.cgi?id=94161
Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: Ben Widawsky <benjamin.widawsky@intel.com>
Tested-by: Timo Aaltonen <tjaalton@ubuntu.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1459860977-27751-1-git-send-email-mika.kuoppala@intel.com
(cherry picked from commit 185c66e57ce725afeb58a3cfa48547706af3a7af)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>