Parser for DMA buffer memory allocations in procfs

Extend the parsing of per-process memory allocations with allocations
related to DMA-buffer RSS.
This is done both for the current RSS and for the high water mark
pullers.

Bug: 424648392
Test: statsd_testdrive 10064
Flag: EXEMPT Atom puller change
Change-Id: I4ac944128d3d104c5377d04ac6c3047933f89011
Signed-off-by: Alessio Balsini <balsini@google.com>