pinctrl: remove mutex lock in groups show

Mutex is locked duplicatly by pinconf_groups_show() and
pin_config_group_get(). It results dead lock. So avoid to lock mutex
in pinconf_groups_show().

Cc: stable@kernel.org
Signed-off-by: Haojian Zhuang <haojian.zhuang@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/pinconf.c

@@ -537,8 +537,6 @@ static int pinconf_groups_show(struct seq_file *s, void *what)
 	seq_puts(s, "Pin config settings per pin group\n");
 	seq_puts(s, "Format: group (name): configs\n");
 
-	mutex_lock(&pinctrl_mutex);
-
 	while (selector < ngroups) {
 		const char *gname = pctlops->get_group_name(pctldev, selector);
 
@@ -549,8 +547,6 @@ static int pinconf_groups_show(struct seq_file *s, void *what)
 		selector++;
 	}
 
-	mutex_unlock(&pinctrl_mutex);
-
 	return 0;
 }