staging: exfat: cleanup spacing for operators

Fixes checkpatch.pl warnings:

  CHECK: spaces preferred around that '-' (ctx:VxV)
  CHECK: spaces preferred around that '+' (ctx:VxV)
  CHECK: spaces preferred around that '*' (ctx:VxV)
  CHECK: spaces preferred around that '|' (ctx:VxV)

Signed-off-by: Valentin Vidic <vvidic@valentin-vidic.from.hr>
Link: https://lore.kernel.org/r/20190908152616.25459-1-vvidic@valentin-vidic.from.hr


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>