samples: usb: wpanusb: Update documentation

Add sample location and fix incorrect goal for the
zephyr-app-commands.

Signed-off-by: Andrei Emeltchenko <andrei.emeltchenko@intel.com>

samples/net/wpanusb/README.rst

@@ -1,6 +1,6 @@
 .. _wpanusb-sample:
 
-WPANUSB sample
+wpanusb sample
 ##############
 
 Overview
@@ -9,14 +9,16 @@ Overview
 This application exports ieee802154 radio over USB to be used in
 other OSes such as Linux.  For Linux, the ieee802154 stack would be
 implemented using the Linux SoftMAC driver.
+This sample can be found under :zephyr_file:`samples/net/wpanusb` in the
+Zephyr project tree.
 
 Requirements
 ************
 
-- a Zephyr WPANUSB enabled board (such as the :ref:`nrf52840_pca10056`)
+- a Zephyr board with supported 802.15.4 radio and supported USB driver
-  connected via USB to a Linux host.
+  (such as the :ref:`nrf52840_pca10056`) connected via USB to a Linux host
-- WPANUSB kernel driver (in the process of being open sourced)
+- wpanusb Linux kernel driver (in the process of being open sourced)
-- IWPAN host tools at [http://wpan.cakelab.org/releases/](http://wpan.cakelab.org/releases/)
+- wpan-tools (available for all Linux distributions)
 
 Building and Running
 ********************
@@ -31,12 +33,12 @@ There are configuration files for various setups in the
 - :file:`overlay-cc2520.conf`
     This overlay config enables support for CC2520
 
-Build the WPANUSB sample like this:
+Build the wpanusb sample for a board:
 
 .. zephyr-app-commands::
    :zephyr-app: samples/net/wpanusb
    :board: <board to use>
-   :conf: <config file to use>
+   :gen-args: -DOVERLAY_CONFIG=<overlay file to use>
    :goals: build
    :compact:
 
@@ -44,9 +46,8 @@ Example building for the Nordic nRF52840 Development Kit:
 
 .. zephyr-app-commands::
    :zephyr-app: samples/net/wpanusb
-   :host-os: unix
    :board: nrf52840_pca10056
-   :goals: run
+   :goals: build
    :compact:
 
 When connected to Linux with wpanusb kernel driver, it is recognized as: