datapath: Rename last_action() as nla_is_last() and move to netlink.h

The original motivation for this change was to allow the helper to be used
in files other than actions.c as part of work on an odp select group
action.

It was as pointed out by Thomas Graf that this helper would be best off
living in netlink.h. Furthermore, I think that the generic nature of this
helper means it is best off in netlink.h regardless of if it is used more
than one .c file or not. Thus, I would like it considered independent of
the work on an odp select group action.

Cc: Thomas Graf <tgraf@suug.ch>
Cc: Pravin Shelar <pshelar@nicira.com>
Cc: Andy Zhou <azhou@nicira.com>
Signed-off-by: Simon Horman <simon.horman@netronome.com>
Acked-by: Thomas Graf <tgraf@noironetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Pravin B Shelar <pshelar@nicira.com>
datapath: Fix few mpls issues.

Found during MPLS upstreaming.  Also sync-up MPLS header files
with upstream code.

Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
datapath: fix coding style.

Kernel datapath code has diverged from upstream code.  This
makes porting patches between these two code bases harder
than it needs to be. Following patch fixes this by fixing
coding style issues on this branch.

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