lib/cbmem: Remove the cbmem_top_init() hook

This hook is unused and with the need for initializing storage to
share cbmem_top over other stages gone, there is likely no future
need for this.

Change-Id: I4ba9daea61b6d7b8949bbd2c4fb71d0a0fa20d93
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/36369
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Nico Huber <nico.h@gmx.de>
Reviewed-by: Michael Niewöhner
Reviewed-by: Aaron Durbin <adurbin@chromium.org>

src/include/cbmem.h

@@ -63,11 +63,6 @@ int cbmem_initialize_id_size(u32 id, u64 size);
 void cbmem_initialize_empty(void);
 void cbmem_initialize_empty_id_size(u32 id, u64 size);
 
-/* Optional hook for platforms to initialize cbmem_top() value. When employed
- * it's called a single time during boot at cbmem initialization/recovery
- * time. */
-void cbmem_top_init(void);
-
 /* Return the top address for dynamic cbmem. The address returned needs to
  * be consistent across romstage and ramstage, and it is required to be
  * below 4GiB for 32bit coreboot builds. On 64bit coreboot builds there's no