msm: camera_v2: isp: Fix ub allocation logic

To overcome vfe overflow issues, modify ub allocation
logic for vfe wm, when we allocate ub proportionally for
pix and rdi, consider min_ub as 96 (Qwords) for pix
interface and 192 (Qwords) for rdi interface.

Change-Id: I924f3f869eab663710ad326b7c2d5f7c84f4af1f
Signed-off-by: Ramesh V <ramev@codeaurora.org>