leds: pca955x: Avoid potential overflow when filling default_label (take 2)

GCC compiler v8.5.0 is not happy about printing
into a too short buffer (when build with `make W=1`):

  drivers/leds/leds-pca955x.c:696:5: note: 'snprintf' output between 2 and 11 bytes into a destination of size 8

Unfortunately this is a false positive from the old GCC versions,
but we may still improve the code by using '%hhu' format specifier
and reduce buffer size by 4 bytes.

Fixes: bd3d149 ("leds: pca955x: Avoid potential overflow when filling default_label")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202506282159.TXfvorYl-lkp@intel.com/
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://lore.kernel.org/r/20250630093906.1715800-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Lee Jones <lee@kernel.org>

Author: andy-shev

drivers/leds/leds-pca955x.c

@@ -587,7 +587,7 @@ static int pca955x_probe(struct i2c_client *client)
 	struct pca955x_platform_data *pdata;
 	bool keep_psc0 = false;
 	bool set_default_label = false;
-	char default_label[8];
+	char default_label[4];
 	int bit, err, reg;
 
 	chip = i2c_get_match_data(client);
@@ -693,7 +693,7 @@ static int pca955x_probe(struct i2c_client *client)
 			}
 
 			if (set_default_label) {
-				snprintf(default_label, sizeof(default_label), "%u", i);
+				snprintf(default_label, sizeof(default_label), "%hhu", i);
 				init_data.default_label = default_label;
 			} else {
 				init_data.default_label = NULL;