drm/i915: Move device_info.has_snoop into the static tables

Currently we define any !llc machine as using snoop instead. However,
some platforms run into trouble using snoop that we would like to
disable, and to do so easily we want to be able to use the static
device_info tables.

v2: Leave the old snoop = !llc as a warning for the time being to check
that all stanzas are filled as either llc or snoop.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170906105653.3665-1-chris@chris-wilson.co.uk