pinctrl: make pinctrl_register() return proper error code

Currently, pinctrl_register() just returns NULL on error, so the
callers can not know the exact reason of the failure.

Some of the pinctrl drivers return -EINVAL, some -ENODEV, and some
-ENOMEM on error of pinctrl_register(), although the error code
might be different from the real cause of the error.

This commit reworks pinctrl_register() to return the appropriate
error code and modifies all of the pinctrl drivers to use IS_ERR()
for the error checking and PTR_ERR() for getting the error code.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Patrice Chotard <patrice.chotard@st.com>
Acked-by: Thierry Reding <treding@nvidia.com>
Acked-by: Heiko Stuebner <heiko@sntech.de>
Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: Lee Jones <lee@kernel.org>
Acked-by: Sören Brinkmann <soren.brinkmann@xilinx.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Ray Jui <rjui@broadcom.com>
Acked-by: Antoine Tenart <antoine.tenart@free-electrons.com>
Acked-by: Hongzhou Yang <hongzhou.yang@mediatek.com>
Acked-by: Wei Chen <Wei.Chen@csr.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
diff --git a/drivers/pinctrl/pinctrl-as3722.c b/drivers/pinctrl/pinctrl-as3722.c
index db0571f..4747e08 100644
--- a/drivers/pinctrl/pinctrl-as3722.c
+++ b/drivers/pinctrl/pinctrl-as3722.c
@@ -586,9 +586,9 @@
 	as3722_pinctrl_desc.npins = ARRAY_SIZE(as3722_pins_desc);
 	as_pci->pctl = pinctrl_register(&as3722_pinctrl_desc,
 					&pdev->dev, as_pci);
-	if (!as_pci->pctl) {
+	if (IS_ERR(as_pci->pctl)) {
 		dev_err(&pdev->dev, "Couldn't register pinctrl driver\n");
-		return -EINVAL;
+		return PTR_ERR(as_pci->pctl);
 	}
 
 	as_pci->gpio_chip = as3722_gpio_chip;