net/openvswitch: remove dup comment in vport.h

Remove the duplicated comment
"/* The following definitions are for users of the vport subsytem: */"
in vport.h

Signed-off-by: Wang Sheng-Hui <shhuiw@gmail.com>
Acked-by: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: David S. Miller <davem@davemloft.net>