msm: camera: isp: Update active flag for RDI for start/stop AXI

RDI stream active flag was not set on start_stream. Hence stop_stream
was returning without wait for stop WM. On return the buffer is
released causing IOMMU page fault. Update the active flag correctly
on start and stop to fix this.

Change-Id: I3872e82df4458f4d30db4845301109f0ae9a9ab7
Signed-off-by: Harsh Shah <harshs@codeaurora.org>