CBMEM northbridges: Remove references to global high_tables_base

Use the new helper function set_top_of_ram() to remove remaining
uses of high_tables_base and _size under northbridge/.

Change-Id: I6b0d9615002ed2aff578c5811d7bd43dd2594453
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: http://review.coreboot.org/3561
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@google.com>
27 files changed