vidc: fix wrong number of slices in slice delivery mode

The slices completed is not matching with the expected number
of slices in frame done. The fix is available in July firmware
release and this commit will have the corresponding video driver
changes.

CRs-fixed: 380629
Change-Id: Ia5c2cce2e95e31deac023a6c855fd385494ee56b
Signed-off-by: Maheshwar Ajja <majja@codeaurora.org>