Fix the following build errors reported by Yinghai Lu:

| In file included from arch/x86/mach-generic/summit.c:16:
| tip/linux-2.6/arch/x86/include/asm/summit/apic.h:
| In function 'cpu_mask_to_apicid_and':
| tip/linux-2.6/arch/x86/include/asm/summit/apic.h:179:
| error: 'GFP_ATOMIC' undeclared (first use in this function)
Reported-by: Yinghai Lu <Yinghai.Lu@Sun.COM>
Signed-off-by: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>