x86: make APIC_init_uniprocessor() more like smp_prepare_cpus()

Impact: cleanup

1. move localise_nmi_watchdog() later
2. change setup_boot_APIC_clock() to setup_boot_clock() for 64-bit

Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>