can: uapi: update CAN-FD frame description

Since an early version of the CAN-FD specification the bit that
defines a CAN-FD frame on the wire, has been renamed from Extended
Data Length (EDL) to FD Frame (FDF).

To avoid confusion, update the struct canfd_frame description in the
UAPI headers accordingly.

Link: https://lore.kernel.org/r/20210517113727.77597-1-mkl@pengutronix.de
Suggested-by: Ayoub Kaanich <kayoub5@live.com>
Acked-by: Oliver Hartkopp <socketcan@hartkopp.net>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

include/uapi/linux/can.h

@@ -123,8 +123,8 @@ struct can_frame {
 /*
  * defined bits for canfd_frame.flags
  *
- * The use of struct canfd_frame implies the Extended Data Length (EDL) bit to
- * be set in the CAN frame bitstream on the wire. The EDL bit switch turns
+ * The use of struct canfd_frame implies the FD Frame (FDF) bit to
+ * be set in the CAN frame bitstream on the wire. The FDF bit switch turns
  * the CAN controllers bitstream processor into the CAN FD mode which creates
  * two new options within the CAN FD frame specification:
  *