drm/xe: Remove vram size info from sysfs

This information is already part of the query IOCTL.
Let's not duplicate it here in the sysfs.

Cc: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>