octeontx2-af: replace deprecated strncpy with strscpy

octeontx2-af: 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 can see that linfo->lmac_type is expected to be NUL-terminated based
on the `... - 1`'s present in the current code. Presumably making room
for a NUL-byte at the end of the buffer.

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 prefer the more idiomatic strscpy usage of (dest, src,
sizeof(dest)) rather than (dest, src, SOME_LEN).

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>
Link: https://lore.kernel.org/r/20231010-strncpy-drivers-net-ethernet-marvell-octeontx2-af-cgx-c-v1-1-a443e18f9de8@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>