fpga: dfl-pci: locate DFLs by PCIe vendor specific capability

A PCIe vendor specific extended capability is introduced by Intel to
specify the start of a number of DFLs.

Signed-off-by: Matthew Gerlach <matthew.gerlach@linux.intel.com>
Signed-off-by: Moritz Fischer <mdf@kernel.org>
Link: https://lore.kernel.org/r/20210107043714.991646-3-mdf@kernel.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>