[IA64] fix section mismatch in arch/ia64/kernel/topology.c

This patch silences:

	WARNING: vmlinux.o(.text+0x44672): Section mismatch in
	reference from the function arch_register_cpu() to the
	function .cpuinit.text:register_cpu()

Changes are based on codes in arch/x86/kernel/topology.c

Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>