openvswitch: Simplify interface ovs_flow_metadata_from_nlattrs()

This is not functional change, this is just code cleanup.

Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: Jesse Gross <jesse@nicira.com>

diff --cc net/openvswitch/datapath.c
Simple merge

diff --cc net/openvswitch/flow.c
Simple merge

diff --cc net/openvswitch/flow.h
Simple merge