can: migrate documentation to restructured text

The kernel documentation is now restructured text. Convert the SocketCAN
documentation and include it in the toplevel kernel documentation.

This patch doesn't do any content change.

All references to can.txt in the code are converted to can.rst.

Signed-off-by: Robert Schwebel <r.schwebel@pengutronix.de>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/vcan.c

@@ -61,7 +61,7 @@ MODULE_ALIAS_RTNL_LINK(DRV_NAME);
 /*
  * CAN test feature:
  * Enable the echo on driver level for testing the CAN core echo modes.
- * See Documentation/networking/can.txt for details.
+ * See Documentation/networking/can.rst for details.
  */
 
 static bool echo; /* echo testing. Default: 0 (Off) */