Add PCI stats

PCI stats abstract the pci device info on compute node for scheduler.
provide better performance than join load from pci device table.

PCI stats contain the available count info for PCI devices with same
spec, ie, the same product_id and verndor_id.and provide method to check
if the requests is supported.

bp:pci-passthrough-base

Change-Id: I8d77c685f774aae22da87be9e822bfd44f0b7a6d
Signed-off-by: Yunhong Jiang <yunhong.jiang@intel.com>
Signed-off-by: Yongli He <yongli.he@intel.com>
Merge "Add PCI stats"