drm/xe: Make xe_mmio_tile_vram_size() static

drm/xe: Make xe_mmio_tile_vram_size() static

During xe_mmio_probe_vram(), we already store the values returned from
xe_mmio_tile_vram_size() into the xe_tile structures.
There is no need to call xe_mmio_tile_vram_size() again later during
setup of the STOLEN region. Just use the values stored in the root tile.

Signed-off-by: Brian Welty <brian.welty@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper at intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>