c2port: replace deprecated strncpy with strscpy

c2port: replace deprecated strncpy with strscpy

`strncpy` is deprecated for use on NUL-terminated destination strings
[1] and as such we should prefer more robust and less ambiguous string
interfaces.

We expect `c2dev->name` to be NUL-terminated based on its usage with
format strings:
|       dev_info(c2dev->dev, "C2 port %s removed\n", c2dev->name);

Moreover, NUL-padding is _not_ required as c2dev is zero-allocated:
|       c2dev = kzalloc(sizeof(struct c2port_device), GFP_KERNEL);

Considering the above, a suitable replacement is `strscpy` [2] due to
the fact that it guarantees NUL-termination on the destination buffer
without unnecessarily NUL-padding.

Let's also drop `C2PORT_NAME_LEN - 1` for `sizeof(dest)` which is more
idiomatic strscpy usage.

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings
Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html
Link: https://github.com/KSPP/linux/issues/90
Cc: linux-hardening@vger.kernel.org
Signed-off-by: Justin Stitt <justinstitt@google.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Link: https://lore.kernel.org/r/20230927-strncpy-drivers-misc-c2port-core-c-v1-1-978f6d220a54@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>