net: dsa: microchip: copy string using strscpy

Prior to this patch ksz_ptp_msg_irq_setup() uses snprintf() to copy
strings. It does so by passing strings as the format argument of
snprintf(). This appears to be safe, due to the absence of format
specifiers in the strings, which are declared within the same function.
But nonetheless GCC 14 warns about it:

.../ksz_ptp.c:1109:55: warning: format string is not a string literal (potentially insecure) [-Wformat-security]
 1109 |         snprintf(ptpmsg_irq->name, sizeof(ptpmsg_irq->name), name[n]);
      |                                                              ^~~~~~~
.../ksz_ptp.c:1109:55: note: treat the string as an argument to avoid this
 1109 |         snprintf(ptpmsg_irq->name, sizeof(ptpmsg_irq->name), name[n]);
      |                                                              ^
      |                                                              "%s",

As what we are really dealing with here is a string copy, it seems make
sense to use a function designed for this purpose. In this case null
padding is not required, so strscpy is appropriate. And as the
destination is an array of fixed size, the 2-argument variant may be used.

Reviewed-by: Daniel Machon <daniel.machon@microchip.com>
Signed-off-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20241014-string-thing-v2-1-b9b29625060a@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/dsa/microchip/ksz_ptp.c

@@ -1106,7 +1106,7 @@ static int ksz_ptp_msg_irq_setup(struct ksz_port *port, u8 n)
 	ptpmsg_irq->port = port;
 	ptpmsg_irq->ts_reg = ops->get_port_addr(port->num, ts_reg[n]);
 
-	snprintf(ptpmsg_irq->name, sizeof(ptpmsg_irq->name), name[n]);
+	strscpy(ptpmsg_irq->name, name[n]);
 
 	ptpmsg_irq->num = irq_find_mapping(port->ptpirq.domain, n);
 	if (ptpmsg_irq->num < 0)