Avoid to invoke VPU decoding without additional data
when we are not specifically in PR28 context
as it improves VC1 issue reported in #41
To do so, Test if frame size (and thus VPU_DEC_ONE_FRM_CONSUMED)
is handled before dealing with m_bytesToBeConsumed
Merge pull request #42 from xbmc-imx6/fixvc1

Improve VC1 decoding