drm/i915/gtt/dg1: add PTE_LM plumbing for GGTT

For the PTEs we get an LM bit, to signal whether the page resides in
SMEM or LMEM.

Based on a patch from Michel Thierry.

BSpec: 45015

Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20210203171231.551338-3-matthew.auld@intel.com


Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>