ANDROID: GKI: mm: add rss counter for unreclaimable pages

Add a per mm rss counter to hold the unreclaimable
pages. This can include the pages allocated by a
task and shared with hardware for DMA etc.

Signed-off-by: Vinayak Menon <vinmenon@codeaurora.org>
Signed-off-by: Will McVicker <willmcvicker@google.com>
(cherry picked from commit ade7f1cd6f26780890cab9ae67f0033f1de432a7)
Bug: 148872640
Change-Id: Iec77d69eca0a4f8f6e23f866c80c0143620fcaf2