msm: vidc: Fix an issue in encoder extradata output buffer index

The buffer requirements are stored based on the buffer type.
The buffer type value could be different from the index of the
buffer. To access the right buffer driver needs to compare the
buffer types and shouldn't use the buffer type as index. This
change fixes the same.

Change-Id: I4d928a1218c2be9349b3970fc3812f9a751452d3
Signed-off-by: Praneeth Paladugu <ppaladug@codeaurora.org>