pinctrl: Use seq_putc() in pinctrl_maps_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>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/core.c

@@ -1732,7 +1732,7 @@ static int pinctrl_maps_show(struct seq_file *s, void *what)
 			break;
 		}
 
-		seq_printf(s, "\n");
+		seq_putc(s, '\n');
 	}
 	mutex_unlock(&pinctrl_maps_mutex);