msm: vidc: Configure work mode 2 based on rate control

Existing code sets work mode as 1 for all encoder usecases.
For VBR and MBR cases, work mode is required to be 2. Hence
set the same based on RC mode.

Change-Id: I0842ddd23750395a84ec87ffa76677675128e301
Signed-off-by: Manikanta Kanamarlapudi <kmanikan@codeaurora.org>