camera: Add support for ZSL on new Samsung devices

 * The camera driver on new Samsung devices requires that we send a
   magic command to the hardware in order to get ZSL behavior with
   continuous preview. On previous devices, this worked as long as the
   "cam_mode" parameter was zero (instead of null) and "camera-mode" is
   set to 1. On JF, we need to do all of these things.
 * The command we need to send is 1508, but I do not know what this
   value actually corresponds to. It was discovered by reverse
   engineering.

Change-Id: I6bccc9cd228784045eef81719892121749af4fa5