net/mlx4_core: replace deprecated strncpy with strscpy

net/mlx4_core: 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 `dst` to be NUL-terminated based on its use with format
strings:
|       mlx4_dbg(dev, "Reporting Driver Version to FW: %s\n", dst);

Moreover, NUL-padding is not required.

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.

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: Saeed Mahameed <saeedm@nvidia.com>
Link: https://lore.kernel.org/r/20231011-strncpy-drivers-net-ethernet-mellanox-mlx4-fw-c-v1-1-4d7b5d34c933@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>