drm/xe: Remove never used code in xe_vm_create()

drm/xe: Remove never used code in xe_vm_create()

Clang is not happy with set but unused variable (this is visible
with `make LLVM=1` build:

  drivers/gpu/drm/xe/xe_vm.c:1462:11: error: variable 'number_tiles' set
  but not used [-Werror,-Wunused-but-set-variable]

The use of this variable was removed in the commit mentioned below as
"Fixes:" but only its declaration and update remain.
It seems like the variable is not used along with the assignment that
does not have side effects as far as I can see.
Remove those altogether.

Fixes: cb99e12ba8cb ("drm/xe: Decouple bind queue last fence from TLB invalidations")
Signed-off-by: Gwan-gyeong Mun <gwan-gyeong.mun@intel.com>
Reviewed-by: Michał Winiarski <michal.winiarski@intel.com>
Link: https://patch.msgid.link/20251105011311.3177875-1-gwan-gyeong.mun@intel.com
Signed-off-by: Michał Winiarski <michal.winiarski@intel.com>