swconfig: add SWITCH_TYPE_LINK and support sending link info to user space

So far we were sending link data as a string. It got some drawbacks:
1) Didn't allow writing clean user space apps reading link state. It was
   needed to do some screen scraping.
2) Forced whole PORT_LINK communication to be string based. Adding
   support for *setting* port link required passing string and parting
   it in the kernel space.

Signed-off-by: Rafał Miłecki <zajec5@gmail.com>

SVN-Revision: 47997

target/linux/generic/files/include/linux/switch.h

@@ -122,6 +122,7 @@ struct switch_dev {
 	struct mutex sw_mutex;
 	struct switch_port *portbuf;
 	struct switch_portmap *portmap;
+	struct switch_port_link linkbuf;
 
 	char buf[128];
 
@@ -148,6 +149,7 @@ struct switch_val {
 		const char *s;
 		u32 i;
 		struct switch_port *ports;
+		struct switch_port_link *link;
 	} value;
 };