pinctrl: fix pinconf_dbg_config_write return type

Have pinconf_dbg_config_write() return a ssize_t. This fixes the following
compilation warning:

  drivers/pinctrl/pinconf.c:617:2: warning: initialization from incompatible pointer type [enabled by default]
  drivers/pinctrl/pinconf.c:617:2: warning: (near initialization for ‘pinconf_dbg_pinconfig_fops.write’) [enabled by default]
Signed-off-by: Vincent Stehlé <vincent.stehle@laposte.net>
Cc: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/pinconf.c

@@ -490,7 +490,7 @@ static int pinconf_dbg_config_print(struct seq_file *s, void *d)
  * <devicename> <state> <pinname> are values that should match the pinctrl-maps
  * <newvalue> reflects the new config and is driver dependant
  */
-static int pinconf_dbg_config_write(struct file *file,
+static ssize_t pinconf_dbg_config_write(struct file *file,
 	const char __user *user_buf, size_t count, loff_t *ppos)
 {
 	struct pinctrl_maps *maps_node;