This patch adds virtualization support description for DFL based
FPGA devices (based on PCIe SRIOV), and introductions to new
interfaces added by new dfl private feature drivers.

[mdf@kernel.org: Fixed up to make it work with new reStructuredText docs]
Signed-off-by: NXu Yilun <yilun.xu@intel.com>
Signed-off-by: NWu Hao <hao.wu@intel.com>
Acked-by: NAlan Tull <atull@kernel.org>
Signed-off-by: NMoritz Fischer <mdf@kernel.org>