msm: camera: isp: Validate packet op-code while checking last flush req

Reject only update packets as part of config if it's request id is
less than last flush req id for that context.

Change-Id: Id5cc971cd23dd07463f767dc01277e8e1d805b99
Signed-off-by: Karthik Anantha Ram <kartanan@codeaurora.org>