switchdev: documentation: fix whitespace issues

Figure 1 is full of whitespaces; fix it

Signed-off-by: Liam Beguin <lbeguin@tycoint.com>
Signed-off-by: Sylvain Lemieux <slemieux@tycoint.com>
Acked-by: Ivan Vecera <ivecera@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>