msm: camera: enable dual camera concurrency

1. There is only one combo csiphy for msm8909,so the single
   csiphy should be initialed twice when two camera started simultaneously.
2. Each stream must configure its own UB respectively,because the length
   and offset of each stream buffer may not be identical.

Change-Id: I0bae42632a47518132384d923774232a4a6afdec
Signed-off-by: Tao Jiang <taojiang@codeaurora.org>