sepolicy: corrected firmware_file file type association

As we no longer us firmware mount on root/system  we are
de-associating  system_file_type form it .
Change-Id: If2a8153436f4ffaa5e5539c09df184a7b9e5fbb8
4 files changed
tree: c48317ed4d0626e0746c4263a86baf815f2256ad
  1. generic/
  2. legacy/
  3. qva/
  4. Android.mk