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
setting the same based on RC mode.

Change-Id: I882807ccc4e0348e2cdfab1e74b80a55a47b754d
Signed-off-by: Vikash Garodia <vgarodia@codeaurora.org>