Fix ia64 build setup_per_cpu_areas() redifinition issue in UP
configuration.  When compiling ia64 kernel in UP configuration, the
following compilation errors are reported:

arch/ia64/kernel/setup.c:860: error: redefinition of 'setup_per_cpu_areas'
include/linux/percpu.h:185: error: previous definition of 'setup_per_cpu_areas' was here

The patch fixes the issue in arch/ia64/kernel/setup.c
Signed-off-by: NFenghua Yu <fenghua.yu@intel.com>
Signed-off-by: NTejun Heo <tj@kernel.org>