msm: camera: isp: Transition to HALT state prior to HW stop

In case of any error IRQs encountered during stop, there is
no need to notify them to UMD since the entire pipeline
would be reset prior to next session start. With this change
we transition to HALT state and then issue stop.

CRs-Fixed: 2825121
Change-Id: I9535439d1a29e3b6f8da968b60e5b2b5bc32c1bf
Signed-off-by: Karthik Anantha Ram <kartanan@codeaurora.org>