drm/i915/skl: Disable coarse power gating up until F0

drm/i915/skl: Disable coarse power gating up until F0

BugLink: http://bugs.launchpad.net/bugs/1527462
There is conflicting info between E0 and F0 steppings
for this workarounds. Trust more authoritative source and
be conservative and extend also for F0.

This prevents numerous (>50) gpu hangs with SKL GT4e
during piglit run.

References: HSD: gen9lp/2134184
Cc: Sagar Arun Kamble <sagar.a.kamble@intel.com>
Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: Sagar Arun Kamble <sagar.a.kamble@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1449505785-20812-1-git-send-email-mika.kuoppala@intel.com
(cherry picked from commit 6686ece19f7446f0e29c77d9e0402e1d0ce10c48)
Cc: stable@vger.kernel.org # v4.3+
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
(cherry picked from commit 344df9809f4521c8c11d67c5ef18764b54358950)
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>