bus/ifpga: add Intel FPGA bus library

bus/ifpga: add Intel FPGA bus library

Defined FPGA-BUS for Acceleration Drivers of AFUs

1. FPGA PCI Scan (1st Scan) follows DPDK UIO/VFIO PCI Scan Process,
probe Intel FPGA Rawdev Driver, it will be covered in following patches.

2. AFU Scan(2nd Scan) bind DPDK driver to FPGA Partial-Bitstream.
This scan is trigged by hotplug of IFPGA Rawdev probe, in this scan
the AFUs will be created and their drivers are also probed.

This patch will introduce rte_afu_device which describe the AFU device
listed in the FPGA-BUS.

Signed-off-by: Rosen Xu <rosen.xu@intel.com>
Signed-off-by: Tianfei Zhang <tianfei.zhang@intel.com>
Reviewed-by: Qi Zhang <qi.z.zhang@intel.com>