Allow mediacodec to allocate from the DMA-BUF system heap

mediacodec currently only has permissions to allocate from ION heaps.
The following permission is required for it to allocate from the
DMA-BUF system heap via the the codec2 allocator.

It resolves the following denial in the sdk_gphone_x86_64-userdebug
target:

01-08 22:43:48.712   337   337 I auditd  : type=1400 audit(0.0:6): avc:
denied { getattr } for comm="android.hardwar"
path="/dev/dma_heap/system-uncached" dev="tmpfs" ino=311
scontext=u:r:mediacodec:s0
tcontext=u:object_r:dmabuf_system_heap_device:s0 tclass=chr_file
permissive=0

Bug: 170887642
Test: make and boot
Change-Id: I5503ed6ffa47a84f614792de866ddafbec0cdcda
1 file changed