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 <[e-mail]>
Acked-by: Charles Keepax <[e-mail]>
Signed-off-by: Linus Walleij <[e-mail]>

drivers/gpio/gpio-wm831x.c

···
 			dev_err(wm831x->dev,
 				"GPIO control %d read failed: %d\n",
 				gpio, reg);
-			seq_printf(s, "\n");
+			seq_putc(s, '\n');
 			continue;
 		}