mm-video: vdec: Fix memory leak in color converter.

When OMX is deinitialized, the color converter buffers stay intact, causing the
available memory pool to have less continuous space available.

Change-Id: Icc2d730d540bae153c9fde36a6f4267ff3f9f088
Merge remote-tracking branch 'cm/cm-11.0' into cm-11.0