Give mediatranscoding access to the DMA-BUF system heap

Fixes the following denials:

avc: denied { getattr } for path="/dev/dma_heap/system" dev="tmpfs"
ino=534 scontext=u:r:mediatranscoding:s0
tcontext=u:object_r:dmabuf_system_heap_device:s0 tclass=chr_file
permissive=0

Bug: 185867872
Test: No more DMA-BUF heap related denials from
CtsMediaTranscodingTestCases

Change-Id: I45b57b45e0db996f08b82618dcd085ba0f7e6ef6
1 file changed