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>
diff --git a/src/mainboard/emulation/qemu-i440fx/northbridge.c b/src/mainboard/emulation/qemu-i440fx/northbridge.c
index 2ea4a68..a2cd37b 100644
--- a/src/mainboard/emulation/qemu-i440fx/northbridge.c
+++ b/src/mainboard/emulation/qemu-i440fx/northbridge.c
@@ -86,9 +86,7 @@
 	}
 
 #if !CONFIG_DYNAMIC_CBMEM
-	/* Leave some space for ACPI, PIRQ and MP tables */
-	high_tables_base = (tomk * 1024) - HIGH_MEMORY_SIZE;
-	high_tables_size = HIGH_MEMORY_SIZE;
+	set_top_of_ram(tomk * 1024);
 #endif
 
 	if (i440fx) {