drm/xe: Move VRAM MM debugfs creation to tile level

drm/xe: Move VRAM MM debugfs creation to tile level

Previously, VRAM TTM resource manager debugfs entries (vram0_mm / vram1_mm)
were created globally in the XE debugfs root directory. But technically,
each tile has an associated VRAM TTM manager, which it can own.
Let's create VRAM memory manager debugfs entries directly under each tile's
debugfs directory for better alignment with the per-tile memory layout.

Signed-off-by: Piotr Piórkowski <piotr.piorkowski@intel.com>
Reviewed-by: Stuart Summers <stuart.summers@intel.com>
Link: https://patch.msgid.link/20251127073643.144379-1-piotr.piorkowski@intel.com
Signed-off-by: Michał Winiarski <michal.winiarski@intel.com>