tools: usb: p9_fwd: wrap USBG shell command examples in literal code blocks

tools: usb: p9_fwd: wrap USBG shell command examples in literal code blocks

Stephen Rothwell reported htmldocs warning when merging usb tree:

Documentation/filesystems/9p.rst:99: ERROR: Unexpected indentation.

That's because Sphinx tries rendering p9_fwd.py output as a grid table
instead.

Wrap shell commands in "USBG Example" section in literal code blocks
to fix above warning and to be in line with rest of commands in the doc.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Closes: https://lore.kernel.org/linux-next/20240905184059.0f30ff9a@canb.auug.org.au/
Fixes: 673f0c3ffc75 ("tools: usb: p9_fwd: add usb gadget packet forwarder script")
Signed-off-by: Bagas Sanjaya <bagasdotme@gmail.com>
Acked-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Link: https://lore.kernel.org/r/20240908113423.158352-1-bagasdotme@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>