drm/i915: Drop address size from ppgtt_type

With the introduction of the separate addressable bits into the device
info, we can remove the conflation of the ppgtt size from the ppgtt
type.

Based on a patch by Bob Paauwe.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Bob Paauwe <bob.j.paauwe@intel.com>
Cc: Matthew Auld <matthew.william.auld@gmail.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190314223839.28258-3-chris@chris-wilson.co.uk