media: dvb: Add cache maintenance when working with SDMX

Input buffer of secure demux running in TZ must be
flushed before secure demux starts processing the data,
while output buffers from secure demux needs to be
invalidated when secure demux finishes processing of
the data.

Change-Id: If87051f2b0027491a6f5cb13f504721e6104bf81
Signed-off-by: Hamad Kadmany <hkadmany@codeaurora.org>