drm/i915: Move load time runtime device info init earlier

This init step accesses the device, but doesn't have any device
specific side effect. It also sets up some platform specific
attributes that may be required early, so move it earlier.

Signed-off-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: http://patchwork.freedesktop.org/patch/msgid/1458128348-15730-7-git-send-email-imre.deak@intel.com