drm/xe: Add NEEDS_2M BO flag

In addition of NEEDS_64K BO flag, add similar one to force 2 MiB
alignment of the buffer objects. Explicitly use this flag during
VF LMEM provisioning as LMTT uses 2 MiB pages and one day we may
drop requirement of allocating pinned objects as contiguous.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: Jonathan Cavitt <jonathan.cavitt@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240715180538.1418-3-michal.wajdeczko@intel.com