datapath: Use ccflags-y instead of deprecated EXTRA_CFLAGS

This allows users to pass in additional compiler flags through the
environment variable EXTRA_CFLAGS, e.g.

   make EXTRA_CFLAGS=-Wno-error=foo V=1

Reported-by: Alexandru Ardelean <ardeleanalex@gmail.com>
Signed-off-by: Thomas Graf <tgraf@noironetworks.com>
Acked-by: Pravin B Shelar <pshelar@nicira.com>
route-table: Remove Unregister.

Since dpif registering for routing table at initialization
there is no need to unregister it. Following patch removes
support for turning routing table notifications on and off.
Due to this change OVS always listens for these
notifications.

Reported-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Acked-by: YAMAMOTO Takashi <yamamoto@valinux.co.jp>