C2VdaBqBlockPool: do not support byte-buffer mode

Currenlty C2VdaBqBlockPool is highly coupled with IGBP.
V4L2DecodeComponent cannot work with the buffers not received from the
IGBP. This CL removes the fallback when the IGBP is not configured.

Bug: 160110407
Test: android.media.cts.AdaptivePlaybackTest
Change-Id: I61e3ad01fb85a7b8003c948a5b3cbba341888d3c