usb_canbus: Initial support for USB to CAN bridge mode

Support a USB interface that shows up as a canbus adapter to linux.
Route both local and real canbus packets over that interface.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

src/Kconfig

@@ -55,22 +55,24 @@ config SERIAL_BAUD
 # Generic configuration options for USB
 config USBSERIAL
     bool
+config USBCANBUS
+    bool
 config USB_VENDOR_ID
     default 0x1d50
 config USB_DEVICE_ID
     default 0x614e
 config USB_SERIAL_NUMBER_CHIPID
-    depends on HAVE_CHIPID && USBSERIAL
+    depends on HAVE_CHIPID && (USBSERIAL || USBCANBUS)
     default y
 config USB_SERIAL_NUMBER
     default "12345"
 
 menu "USB ids"
-    depends on USBSERIAL && LOW_LEVEL_OPTIONS
+    depends on (USBSERIAL || USBCANBUS) && LOW_LEVEL_OPTIONS
 config USB_VENDOR_ID
-    hex "USB vendor ID"
+    hex "USB vendor ID" if USBSERIAL
 config USB_DEVICE_ID
-    hex "USB device ID"
+    hex "USB device ID" if USBSERIAL
 config USB_SERIAL_NUMBER_CHIPID
     bool "USB serial number from CHIPID" if HAVE_CHIPID
 config USB_SERIAL_NUMBER
@@ -82,7 +84,7 @@ config CANSERIAL
     bool
 config CANBUS
     bool
-    default y if CANSERIAL
+    default y if CANSERIAL || USBCANBUS
 config CANBUS_FREQUENCY
     int "CAN bus speed" if LOW_LEVEL_OPTIONS && CANBUS
     default 500000