Nfb: Add README

Author: Pavel Siska

src/plugins/input/nfb/README.md

@@ -0,0 +1,10 @@
+# NFB (input plugin)
+
+Receive packets over nfb (Netcope FPGA Board). Requires a special network card with compatible
+firmware for high-speed packet processing. Suitable for speeds of 100 Gbps and above.
+
+## Parameters
+```
+  d, dev=PATH    Path to the NFB device to be used and queue ID. (required)
+                 Typically /dev/nfbX:ID or /dev/nfb/by-pci-slot/.... [path:id]
+````