net: introduce generic switch devices support

The goal of this is to provide a possibility to support various switch
chips. Drivers should implement relevant ndos to do so. Now there is
only one ndo defined:
- for getting physical switch id is in place.

Note that user can use random port netdevice to access the switch.

Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Reviewed-by: Thomas Graf <tgraf@suug.ch>
Acked-by: Andy Gospodarek <gospo@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/Kconfig b/net/Kconfig
index 99815b5..ff9ffc1 100644
--- a/net/Kconfig
+++ b/net/Kconfig
@@ -228,6 +228,7 @@
 source "net/netlink/Kconfig"
 source "net/mpls/Kconfig"
 source "net/hsr/Kconfig"
+source "net/switchdev/Kconfig"
 
 config RPS
 	boolean