can: slcan: change every `slc' occurrence in `slcan'

In the driver there are parts of code where the prefix `slc' is used and
others where the prefix `slcan' is used instead. The patch replaces
every occurrence of `slc' with `slcan', except for the netdev functions
where, to avoid compilation conflicts, it was necessary to replace `slc'
with `slcan_netdev'.

The patch does not make any functional changes.
Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
Link: https://lore.kernel.org/all/20220728070254.267974-5-dario.binacchi@amarulasolutions.comSigned-off-by: Marc Kleine-Budde <mkl@pengutronix.de>