purge struct page usage

The only users of struct page treat it like a straight 4k buffer,
so inline the logic so it is just a 4k buffer.

BUG=chromium:878440
TEST=build works

Change-Id: I3e1695f2509b003d31ac70d1d3783f5cee1941c2
Reviewed-on: https://chromium-review.googlesource.com/1215183
Commit-Ready: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Jorge Lucangeli Obes <jorgelo@chromium.org>
5 files changed