net/softnic: support service cores

net/softnic: support service cores

Add support to run the Soft NIC device on service cores, based on the
value of the sc parameter:

0: The current Soft NIC device is run explicitly by the application. The
   firmware creates one or several pipelines for this dev and maps them
   to CPU cores that should not be service cores. The app is required to
   call rte_pmd_softnic_run() to make this dev work.

1 (default): The current device is run on the service cores transparently
   to the app. The firmware creates one or several pipelines for this dev
   current device and maps them to CPU cores that should be service cores.
   Each of these service cores is calling rte_pmd_softnic_run()
   in order to make this dev work with no app intervention.

Signed-off-by: Cristian Dumitrescu <cristian.dumitrescu@intel.com>
Signed-off-by: Jasvinder Singh <jasvinder.singh@intel.com>