CBMEM: Backup top_of_ram instead of cbmem_toc

AMD northbridges have a complex way to resolve top_of_ram.
Once it is resolved, it is stored in NVRAM to be used on resume.

TODO: Redesign these get_top_of_ram() functions from scratch.

Change-Id: I3cceb7e9b8b07620dacf138e99f98dc818c65341
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: http://review.coreboot.org/3557
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@google.com>

src/include/cbmem.h

@@ -132,8 +132,8 @@ u64 cbmem_entry_size(const struct cbmem_entry *entry);
 #ifndef __PRE_RAM__
 extern uint64_t high_tables_base, high_tables_size;
 void set_top_of_ram(uint64_t ramtop);
+void backup_top_of_ram(uint64_t ramtop);
 void cbmem_late_set_table(uint64_t base, uint64_t size);
-void set_cbmem_toc(struct cbmem_entry *);
 int cbmem_base_check(void);
 #endif