powerpc/smp: Remove unused smp_ops->cpu_enable()

Remove the last remnants of cpu_enable(), everybody uses the normal
__cpu_up() path now

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/platforms/powermac/smp.c

@@ -923,8 +923,6 @@ struct smp_ops_t core99_smp_ops = {
 # if defined(CONFIG_PPC64)
 	.cpu_disable	= generic_cpu_disable,
 	.cpu_die	= generic_cpu_die,
-	/* intentionally do *NOT* assign cpu_enable,
-	 * the generic code will use kick_cpu then! */
 # endif
 #endif
 };