recovery: Add fstools

 * Create a new "fstools" target which aggregates all of our filesystem
   tools into a single multi-call binary. This reduces the overall
   recovery image size by a megabyte, and also removes GPL code from the
   main recovery binary.

 * Remove stand alone mkfs.f2fs.

Change-Id: I5fc2a61d564915085071ccbbcb3136f45c640a60