msm: camera: Fix for the bus overflow issue

Support only 2 streams from the VFE, which need only 4 VFE WM.
We divide the UB buffer(1024 * 128 bits) equally into 4 VFE WM and
stats WM.

Correct the offset of burst length in VFE register while writing to HW.
Burst length corresponds to the number of data bytes written at a time.

Change-Id: I82d1b88f499f4572bd58ca29c7cc1a74615554a7
Signed-off-by: Nagesh Subba Reddy <nageshsreddy@codeaurora.org>