x86: use apic_*_around instead of apic_write in x86_64

This patch replaces apic_read() for apic_read_around()
and apic_write for apic_write_around() in smpboot_64.c
We do it to have a common usage between x86_64 and i386.
In the former, it will always simply expand to apic_write

Signed-off-by: Glauber Costa <gcosta@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>