PCI: Add pci_dev_show_local_cpu() to simplify code

local_cpus_show() and local_cpulist_show() are almost the same.
This adds a new helper function, pci_dev_show_local_cpu(), to simplify
code.

The same strategy is already used by cpuaffinity_show() and
cpulistaffinity_show().

Signed-off-by: Yijing Wang <wangyijing@huawei.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>