bna: replace deprecated strncpy with strscpy_pad

bna: replace deprecated strncpy with strscpy_pad

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

bfa_ioc_get_adapter_manufacturer() simply copies a string literal into
`manufacturer`.

Another implementation of bfa_ioc_get_adapter_manufacturer() from
drivers/scsi/bfa/bfa_ioc.c uses memset + strscpy:
|	void
|	bfa_ioc_get_adapter_manufacturer(struct bfa_ioc_s *ioc, char *manufacturer)
|	{
|		memset((void *)manufacturer, 0, BFA_ADAPTER_MFG_NAME_LEN);
|			strscpy(manufacturer, BFA_MFG_NAME, BFA_ADAPTER_MFG_NAME_LEN);
|	}

Let's use `strscpy_pad` to eliminate some redundant work while still
NUL-terminating and NUL-padding the destination buffer.

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings
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/20231009-strncpy-drivers-net-ethernet-brocade-bna-bfa_ioc-c-v2-1-78e0f47985d3@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>