pinctrl: use list_add_tail instead of list_add

This mostly makes debugfs files print things in the order that they
were added or acquired, which just feels a little more consistent.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
diff --git a/drivers/pinctrl/pinmux.c b/drivers/pinctrl/pinmux.c
index fe4a007..5a09cd2 100644
--- a/drivers/pinctrl/pinmux.c
+++ b/drivers/pinctrl/pinmux.c
@@ -480,7 +480,7 @@
 		kfree(grp);
 		return ret;
 	}
-	list_add(&grp->node, &p->groups);
+	list_add_tail(&grp->node, &p->groups);
 
 	return 0;
 }