usertools: define DPDK PCI functional device

usertools: define DPDK PCI functional device

This patch creates the framework to define the DPDK PCI functional
device by specifying the pci attributes like Vendor ID, Device ID,
Sub Vendor ID, Sub Device ID and Class.This enables a flexible way to
add DPDK function devices based on PCI attributes.

Crypto devices can belong to Encryption class(0x10) or Processor
class(0x0b) based on the vendor preference.

Using this framework, The above disparity can be encoded in the following
format

encryption_class = [{'Class': '10', 'Vendor': None,
                     'Device': None, 'SVendor': None, 'SDevice': None}]

intel_processor_class = [{'Class': '0b', 'Vendor': '8086', 'Device': None,
                    'SVendor': None, 'SDevice': None}]

crypto_devices = [encryption_class, intel_processor_class]

Signed-off-by: Guduri Prathyusha <gprathyusha@caviumnetworks.com>
Signed-off-by: Jerin Jacob <jerin.jacob@caviumnetworks.com>