Remove obsolete empy macro definition

In the early days of v2 the (e.g.) #ifdef SMP style was frowned upon in
some quarters.

Hence, empty definitions of functions were created. This
particular function, possibly the last remaining example,
was no longer even being used anywhere.

Signed-off-by: Ron Minnich <rminnich@gmail.com>

src/cpu/x86/lapic/lapic_cpu_init.c

@@ -476,8 +476,6 @@ static void wait_other_cpus_stop(struct bus *cpu_bus)
 	printk(BIOS_DEBUG, "All AP CPUs stopped (%ld loops)\n", loopcount);
 }
 
-#else /* CONFIG_SMP */
-#define initialize_other_cpus(root) do {} while(0)
 #endif /* CONFIG_SMP */
 
 void initialize_cpus(struct bus *cpu_bus)