raw/ifpga: add miscellaneous APIs

raw/ifpga: add miscellaneous APIs

Below miscellaneous APIs are used to implement OPAE application.
1. rte_pmd_ifpga_get_pci_bus() get PCI bus ifpga driver registered.
2. rte_pmd_ifpga_partial_reconfigure() do partial reconfiguration.
3. rte_pmd_ifpga_cleanup() free software resources allocated by driver.
4. rte_pmd_ifpga_set_rsu_status() set status of rsu process.

Signed-off-by: Wei Huang <wei.huang@intel.com>
Acked-by: Tianfei Zhang <tianfei.zhang@intel.com>
Acked-by: Rosen Xu <rosen.xu@intel.com>