drivers: media : demux : Fix demux test case failures

In recent meta builds, kernel crash is observed while running
demux test unit cases. Crash is observed for ION_IOC_INV_CACHES
operation on buffers allocated from qseecom heap. since these
operations are not supported disable the functionality.

Change-Id: If64bed108f187501cb4b203efad0666422f4307a
Signed-off-by: Udaya Bhaskara Reddy Mallavarapu <udaym@codeaurora.org>