can: netlink: document which symbols are FD specific

can: netlink: document which symbols are FD specific

The CAN XL netlink interface will also have data bitrate and TDC
parameters. The current FD parameters do not have a prefix in their
names to differentiate them.

Because the netlink interface is part of the UAPI, it is unfortunately
not feasible to rename the existing symbols to add an FD_ prefix. The
best alternative is to add a comment for each of the symbols to notify
the reader of which parts are CAN FD specific.

While at it, fix a typo: transiver -> transceiver.

Signed-off-by: Vincent Mailhol <mailhol@kernel.org>
Link: https://patch.msgid.link/20250923-canxl-netlink-prep-v4-3-e720d28f66fe@kernel.org
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>