msm: vidc: recalculate buffer counts based on frame rate

Encoder buffer requirement changes based on frame rate or
operating rate (HFR/HSR usecase) and hence recalculate
buffer counts when client set frame rate or operating rate.

Change-Id: I7b421524f319a4fde8b153dcd5c3bde123c5ccf9
Signed-off-by: Maheshwar Ajja <majja@codeaurora.org>