kernel.te: fix MTP sync

STEPS TO REPRODUCE:
  1. Connect the device to Mac.
  2. Switch to AFT.
  3. Now AFT on Mac will show the device contents.
  4. Now drag and drop the file to device and observe.

EXPECTED RESULTS:
  Should able to copy.

OBSERVED RESULTS:
  Showing can not copy file and on clicking ok,
  It shows device storage can not connect and close the AFT.

Addresses the following denial:

  W kworker/u:11: type=1400 audit(0.0:729): avc: denied { use } for path="/storage/emulated/0/Download/song2.mp3" dev="fuse" ino=143 scontext=u:r:kernel:s0 tcontext=u:r:untrusted_app:s0:c512,c768 tclass=fd
  12310 12530 E MtpRequestPacket: Malformed MTP request packet

ps -Z entry:
  u:r:untrusted_app:s0:c512,c768 u0_a6     12310 203   android.process.media

Bug: 15835289
Change-Id: I47b653507f8d4089b31254c19f44706077e2e96a