ANDROID: GKI: mm: export mm_trace_rss_stat for modules to report RSS changes

RSS changes are reported by calling {add|dec|inc}_mm_counter which
in turn call mm_trace_rss_stat. Export mm_trace_rss_stat to allow
modules to report RSS changes.

Bug: 153945060
Bug: 153826075
Bug: 153823050
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Change-Id: I4d77b88d9cd9b3f62d75975fa059d0b9bbaeae0a