leds: lp3952: 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 `dest` to be NUL-terminated due to its use with dev_err.

lp3952_get_label()'s  dest argument is priv->leds[i].name:
|    acpi_ret = lp3952_get_label(&priv->client->dev, led_name_hdl[i],
|                                priv->leds[i].name);
... which is then assigned to:
|    priv->leds[i].cdev.name = priv->leds[i].name;
... which is used with a format string
|    dev_err(&priv->client->dev,
|            "couldn't register LED %s\n",
|            priv->leds[i].cdev.name);

There is no indication that NUL-padding is required but if it is let's
opt for strscpy_pad.

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: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20230922-strncpy-drivers-leds-leds-lp3952-c-v1-1-4941d6f60ca4@google.com
Signed-off-by: Lee Jones <lee@kernel.org>

drivers/leds/leds-lp3952.c

@@ -101,7 +101,7 @@ static int lp3952_get_label(struct device *dev, const char *label, char *dest)
 	if (ret)
 		return ret;
 
-	strncpy(dest, str, LP3952_LABEL_MAX_LEN);
+	strscpy(dest, str, LP3952_LABEL_MAX_LEN);
 	return 0;
 }