drm/i915: power_domains_init sort platforms newer-to-older

No functional change.

Just sorting this "if" block from newer to older platform.

v2: Fix few positions (Ville)

Cc: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181022171526.15641-4-rodrigo.vivi@intel.com