CBMEM: Do not use get_top_of_ram() with DYNAMIC_CBMEM

The name was always obscure and confusing. Instead define cbmem_top()
directly in the chipset code for x86 like on ARMs.

TODO: Check TSEG alignment, it used for MTRR programming.

Change-Id: Ibbe5f05ab9c7d87d09caa673766cd17d192cd045
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: http://review.coreboot.org/7888
Tested-by: build bot (Jenkins)
Reviewed-by: Aaron Durbin <adurbin@google.com>

src/mainboard/emulation/qemu-i440fx/memory.c

@@ -40,7 +40,7 @@ static unsigned long qemu_get_memory_size(void)
 	return tomk;
 }
 
-unsigned long get_top_of_ram(void)
+void *cbmem_top(void)
 {
-	return qemu_get_memory_size() * 1024;
+	return (void *) (qemu_get_memory_size() * 1024);
 }