Add const to ProcessMemory pointers from ProcessReaderLinux::Memory().
This code is ifdef'd to only build on ARM/MIPS.
Change-Id: I93983a83d06bd5bd338b93babdb326fa94925c53
Reviewed-on: https://chromium-review.googlesource.com/c/1341228
Reviewed-by: Mark Mentovai <mark@chromium.org>
Commit-Queue: Vlad Tsyrklevich <vtsyrklevich@chromium.org>