sh: native_cpu_disable() build error when CONFIG_HOTPLUG_CPU=n

arch/sh/kernel/smp.c:164: error: conflicting types for 'native_cpu_disable'
/home/matt/src/kernels/sh-2.6/arch/sh/include/asm/smp.h:48: error: previous declaration of 'native_cpu_disable' was here

Signed-off-by: Matt Fleming <matt@console-pimps.org>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>