msm: camera: isp: Change csid stop sequence during flush

This change takes care of a race which we see when we halt master
csid immediately and slave csid halt to follow. In some scenarios
after master csid halt, slave gives violation errors.
With this change we are first changing the mode of slave to master
then issue halt commands to both master and slave.

CRs-Fixed: 2662825
Change-Id: Id5cd7e1bdf469f43da23af151b99c9f481830cfa
Signed-off-by: Vikram Sharma <vikramsa@codeaurora.org>