msm: camera: reqmgr: Check next req slot at SOF

While checking next slot, if CRM does not find new
request scheduled by UMD, it will assume no new req
and go ahead to only finish the low pipeline delay
module with old request.
Move next req slot checking to SOF, so that CRM is
given larger time slot to receive frame request and
improve FPS consistency.

CRs-fixed: 2096550
Change-Id: Ic317e7ab70498d4d8f87438e80cad1fcb8a610fd
Signed-off-by: Junzhe Zou <jnzhezou@codeaurora.org>