msm: camera: reject request id earlier than last flush request

UMD sends the last request id it expects to flush along with the
flush command and KMD saves it in its own structure. KMD should
recognize the request packets needed to be flushed according to the
request id and reject them.

Change-Id: I73547f0951a9bed4c402705f2f947041c7027d52
Signed-off-by: Junzhe Zou <jnzhezou@codeaurora.org>