drm/xe/stolen: lower the default alignment

No need to be so aggressive here. The upper layers will already apply
the needed alignment, plus some allocations might wish to skip it. Main
issue is that we might want to have start/end bias range which doesn't
match the default alignment which is rejected by the allocator.

Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240412150301.273344-3-matthew.auld@intel.com