libmix: Exclude the number of actual buffer needed calculation for AVC in BYT

BZ: 146862

On MFLD/CTP/MERR platforms, extra buffers are allocated for the encoder and
decoder buffer sharing in the WiDi use cases. Two extra buffers are needed
for native window buffer cycling. The buffer numbers have been set as a fixed
value in LibMIX. But on Baytrail platforms, these buffers are no longer needed.

Change-Id: I5465930eca6ca491b62f4da267f6bcd097dc49f0
Signed-off-by: Gu, Wangyi <wangyi.gu@intel.com>
4 files changed