xilinx: v4l: m2m: Set default mode for framebuffer IP

xilinx: v4l: m2m: Set default mode for framebuffer IP

- Set the framebuffer IP to default mode instead of auto-restart
  mode for mem2mem usecases due to reason explained below:

- By framebuffer IP is programmed by driver to use a special mode
  called auto_restart mode or free-running mode in which core processes
  data periodically irrespective of input rate.

- So in this scenario, if input is stalled for sometime,
  then framebuffer IP will still process with previous data
  and transmit/receive the DMA descriptors.

- This behaviour of auto_restart or free-running mode is fine for
  streaming usecases where display device needs to be provided
  with data at a consistent rate but is not acceptable for mem2mem usecases
  where output needs to have exact 1-to-1 relationship with input
  without any duplication of frames.

- Furthermore this gives a performance benefit for mem2mem usecases
  as the default mode doesn't require to stage a descriptor and
  instead the active descriptor can be marked as complete after
  interrupt is received to process next descriptor.

Signed-off-by: Devarsh Thakkar <devarsh.thakkar@xilinx.com>
Reviewed-by: Satish Kumar Nagireddy <satish.nagireddy.nagireddy@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>