Impact: build fix

Fujita Tomonori reported:

 drivers/pci/probe.c: In function 'pci_bus_show_cpuaffinity':
 drivers/pci/probe.c:56: error: implicit declaration of function 'cpumask_from_node'
 drivers/pci/probe.c:56: warning: pointer/integer type mismatch in conditional expression
 make[3]: *** [drivers/pci/probe.o] Error 1
 make[2]: *** [drivers/pci] Error 2

FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Signed-off-by: Ingo Molnar <mingo@elte.hu>