gpio-wm831x: Use seq_putc() in wm831x_gpio_dbg_show()

A single character (line break) should be put into a sequence.
Thus use the corresponding function "seq_putc".

This issue was detected by using the Coccinelle software.
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Acked-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-wm831x.c

@@ -182,7 +182,7 @@ static void wm831x_gpio_dbg_show(struct seq_file *s, struct gpio_chip *chip)
 			dev_err(wm831x->dev,
 				"GPIO control %d read failed: %d\n",
 				gpio, reg);
-			seq_printf(s, "\n");
+			seq_putc(s, '\n');
 			continue;
 		}