net/smc: Make SMC statistics network namespace aware

Make the gathered SMC statistics network namespace aware, for each
namespace collect an own set of statistic information.

Signed-off-by: Guvenc Gulce <guvenc@linux.ibm.com>
Signed-off-by: Karsten Graul <kgraul@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>