msm: camera: cdm: Add a check for fifo list in cdm workqueue

CDM workqueue stores the last fifo bl tag done entry
for which it's got scheduled. There is possibility
that flush can execute before workqueue and remove
all the fifo entries. This can skip the work for new
requests if new bl tag matches with last bl tag done
entry and cdm don't send notification to clients.

Add a check to validate fifo list for empty entry
in cdm workqueue function.

CRs-Fixed: 2653649
Change-Id: I788f6d1e4c1c011a2a9ed690ddeff2b1bde0e569
Signed-off-by: Alok Chauhan <alokc@codeaurora.org>