IB/hfi1: Replace deprecated strncpy

IB/hfi1: Replace deprecated strncpy

`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 see that `buf` is expected to be NUL-terminated based on it's use
within a trace event wherein `is_misc_err_name` and `is_various_name`
map to `is_name` through `is_table`:
| TRACE_EVENT(hfi1_interrupt,
| 	    TP_PROTO(struct hfi1_devdata *dd, const struct is_table *is_entry,
| 		     int src),
| 	    TP_ARGS(dd, is_entry, src),
| 	    TP_STRUCT__entry(DD_DEV_ENTRY(dd)
| 			     __array(char, buf, 64)
| 			     __field(int, src)
| 			     ),
| 	    TP_fast_assign(DD_DEV_ASSIGN(dd);
| 			   is_entry->is_name(__entry->buf, 64,
| 					     src - is_entry->start);
| 			   __entry->src = src;
| 			   ),
| 	    TP_printk("[%s] source: %s [%d]", __get_str(dev), __entry->buf,
| 		      __entry->src)
| );

Considering the above, a suitable replacement is `strscpy_pad` due to
the fact that it guarantees NUL-termination on the destination buffer
while maintaining the NUL-padding behavior that strncpy provides.

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings
Link: https://github.com/KSPP/linux/issues/90
Cc: linux-hardening@vger.kernel.org
Signed-off-by: Justin Stitt <justinstitt@google.com>
Link: https://lore.kernel.org/r/20230921-strncpy-drivers-infiniband-hw-hfi1-chip-c-v1-1-37afcf4964d9@google.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>