drm/i915/kbl: KBL also needs to run the SAGV code

According to BSpec, it's the "core CPUs" that need the code, which
means SKL and KBL, but not BXT.

I don't have a KBL to test this patch on it.

v2: Only SKL should have I915_SAGV_NOT_CONTROLLED.

Cc: stable@vger.kernel.org
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1474578035-424-4-git-send-email-paulo.r.zanoni@intel.com