drm/xe: Interface xe drm client with fdinfo interface

DRM core driver has introduced recently fdinfo interface to
show memory stats of individual drm client. Lets interface
xe drm client to fdinfo interface.

V2:
  - cover call to xe_drm_client_fdinfo under PROC_FS

Reviewed-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Signed-off-by: Tejas Upadhyay <tejas.upadhyay@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>