hamradio: baycom: replace strcpy() with strscpy()

The strcpy() function has been deprecated and replaced with strscpy().
There is an effort to make this change treewide:
https://github.com/KSPP/linux/issues/88

.

Signed-off-by: Ethan Carter Edwards <ethan@ethancedwards.com>
Reviewed-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://patch.msgid.link/3qo3fbrak7undfgocsi2s74v4uyjbylpdqhie4dohfoh4welfn@joq7up65ug6v


Signed-off-by: Jakub Kicinski <kuba@kernel.org>