drm/i915/gen9: Enable must set chicken bits in config0 reg

The bspec states that these must be set in CONFIG0 for all gen9.

v2: rebase
v3: fix spacing (Matthew)

References: HSD#2134995
Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: Matthew Auld <matthew.auld@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1465309159-30531-13-git-send-email-mika.kuoppala@intel.com