drm/i915: Extract DIMM info on GLK too

The BXT code for parsing DIMM info works for GLK too. Let's
dig it out even if we might not need it immediately.

Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190306203551.24592-7-ville.syrjala@linux.intel.com