msm: vidc: refine firmware cycle calculation

- Dynamically calculate firmware cycle overhead for
  vpp_cycles, instead of using fixed 1.05.
- Consider firmware cycle for ar50 also.
- Refine vsp bw voting for 1-stage mode.

CRs-Fixed: 2384822
Change-Id: I7dd4b1bd7877ae1a9e470bc4a1604cb16dff84c8
Signed-off-by: Qiwei Liu <qiweil@codeaurora.org>