msm: vidc: Enhance the buffer count exchange model

Use extended controls to exchange the buffer counts between
clients and driver. This will give more flexibility for clients
to set the buffer counts.

CRs-Fixed: 2022735
Change-Id: I2e056aa3e83bd47f9b0444775f579f2b7e1d396c
Signed-off-by: Praneeth Paladugu <ppaladug@codeaurora.org>