Move cpus_ready_for_init() to AMD K8

The function is a noop for all but amd/serengeti_cheetah.

Change-Id: I09e2e710aa964c2f31e35fcea4f14856cc1e1dca
Signed-off-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
Reviewed-on: http://review.coreboot.org/1184
Tested-by: build bot (Jenkins)
Reviewed-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>

src/include/cpu/cpu.h

@@ -9,12 +9,6 @@ struct bus;
 void initialize_cpus(struct bus *cpu_bus);
 void secondary_cpu_init(void);
 
-#if !CONFIG_WAIT_BEFORE_CPUS_INIT
-	#define cpus_ready_for_init() do {} while(0)
-#else
-	void cpus_ready_for_init(void);
-#endif
-
 #if CONFIG_HAVE_SMI_HANDLER
 void smm_init(void);
 void smm_lock(void);