msm: camera: Remove stream_cnt from msm video device

Remove stream_cnt from struct msm_video_device
and reuse the atomic_t variable opened for streamid
generation using bit masking.

Change-Id: I32245231fdb01e2dd24930953914b8a8f48daa63
Signed-off-by: Hariram Purushothaman <hpurus@codeaurora.org>