[CAN]: Add virtual CAN netdevice driver

This patch adds the virtual CAN bus (vcan) network driver.
The vcan device is just a loopback device for CAN frames, no
real CAN hardware is involved.

Signed-off-by: Oliver Hartkopp <oliver.hartkopp@volkswagen.de>
Signed-off-by: Urs Thuermann <urs.thuermann@volkswagen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/can/Kconfig

@@ -0,0 +1,25 @@
+menu "CAN Device Drivers"
+	depends on CAN
+
+config CAN_VCAN
+	tristate "Virtual Local CAN Interface (vcan)"
+	depends on CAN
+	default N
+	---help---
+	  Similar to the network loopback devices, vcan offers a
+	  virtual local CAN interface.
+
+	  This driver can also be built as a module.  If so, the module
+	  will be called vcan.
+
+config CAN_DEBUG_DEVICES
+	bool "CAN devices debugging messages"
+	depends on CAN
+	default N
+	---help---
+	  Say Y here if you want the CAN device drivers to produce a bunch of
+	  debug messages to the system log.  Select this if you are having
+	  a problem with CAN support and want to see more of what is going
+	  on.
+
+endmenu