dpdk: only look at PCI information on PCI devices

dpdk: only look at PCI information on PCI devices

The rte_device is use as a base type of all DPDK devices.
It is not valid to use container_of to find PCI information
unless the bus of the rte_device is pci. Otherwise, the
pointer is looking at some other data, which may or may not
be zero.

This change introduces a helper function to get rte_pci_device
pointer. If device is on PCI bus it returns pointer to
rte_pci_device info, otherwise it returns NULL.

Change-Id: Ia7446006bb93a7a54844969f3b3dd3b918890dfd
Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>