ionic: 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.

NUL-padding is not needed due to `ident` being memset'd to 0 just before
the copy.

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 [1]
Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
Link: https://github.com/KSPP/linux/issues/90


Signed-off-by: Justin Stitt <justinstitt@google.com>
Reviewed-by: Shannon Nelson <shannon.nelson@amd.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20231011-strncpy-drivers-net-ethernet-pensando-ionic-ionic_main-c-v1-1-23c62a16ff58@google.com


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