openvswitch: Fix build failure.

Add dependency on INET to fix following build error. I have also
fixed MPLS dependency.

ERROR: "ip_route_output_flow" [net/openvswitch/openvswitch.ko]
undefined!
make[1]: *** [__modpost] Error 1

Reported-by: Jim Davis <jim.epost@gmail.com>
Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: David S. Miller <davem@davemloft.net>