net: ax88796c: replace deprecated strncpy with strscpy

net: ax88796c: 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.

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

It should be noted that there doesn't currently exist a bug here as
DRV_NAME is a small string literal which means no overread bugs are
present.

Also to note, other ethernet drivers are using strscpy in a similar
pattern:
|       dec/tulip/tulip_core.c
|       861:    strscpy(info->driver, DRV_NAME, sizeof(info->driver));
|
|       8390/ax88796.c
|       582:    strscpy(info->driver, DRV_NAME, sizeof(info->driver));
|
|       dec/tulip/dmfe.c
|       1077:   strscpy(info->driver, DRV_NAME, sizeof(info->driver));
|
|       8390/etherh.c
|       558:    strscpy(info->driver, DRV_NAME, sizeof(info->driver));

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
Signed-off-by: Justin Stitt <justinstitt@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Lukasz Stelmach <l.stelmach@samsung.com>
Link: https://lore.kernel.org/r/20231005-strncpy-drivers-net-ethernet-asix-ax88796c_ioctl-c-v1-1-6fafdc38b170@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>