openvswitch: Remove redundant tcp_flags code.

These two cases used to be treated differently for IPv4/IPv6,
but they are now identical.

Signed-off-by: Joe Stringer <joestringer@nicira.com>
Acked-by: Jarno Rajahalme <jrajahalme@nicira.com>
Signed-off-by: Pravin B Shelar <pshelar@nicira.com>