clean up and make nmi_32/64.c more similar.
- white space and coding style clean up.
- nmi_cpu_busy is available on CONFIG_SMP.
- move functions __acpi_nmi_enable, acpi_nmi_enable,
  __acpi_nmi_disable and acpi_nmi_disable.
- make variables name more similar.
Signed-off-by: NHiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>