Documentation: networking: switchdev: separate bulleted items with new line

It looks like "make htmldocs" produces this warning:
Documentation/networking/switchdev.rst:482: WARNING: Unexpected indentation.

Fixes: 0f22ad45 ("Documentation: networking: switchdev: clarify device driver behavior")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>