Documentation: fpga: dfl: add link address of feature id table

This patch adds the link address of feature id table in documentation.

Signed-off-by: Tianfei zhang <tianfei.zhang@intel.com>
Reviewed-by: Matthew Gerlach <matthew.gerlach@linux.intel.com>
Acked-by: Moritz Fischer <mdf@kernel.org>
Acked-by: Wu Hao <hao.wu@intel.com>
Link: https://lore.kernel.org/r/20220419032942.427429-3-tianfei.zhang@intel.com


Signed-off-by: Xu Yilun <yilun.xu@intel.com>