Camera2: Revert ZSL burst mode

* Was added in http://review.cyanogenmod.org/#/c/60993/
  No idea why, as afaik ZSL burst was already supported and working

* The above commit caused burst mode not working. No matter how many shots
  you select, only 1 is taken. Reverting it, everything is fine.

Change-Id: I6d89707e1b25987ab4b5a184a9e93bd254d34a33