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: NMasahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: NPatrice Chotard <patrice.chotard@st.com>
Acked-by: NThierry Reding <treding@nvidia.com>
Acked-by: NHeiko Stuebner <heiko@sntech.de>
Tested-by: NMika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: NMika Westerberg <mika.westerberg@linux.intel.com>
Acked-by: NLee Jones <lee@kernel.org>
Acked-by: NSören Brinkmann <soren.brinkmann@xilinx.com>
Acked-by: NLaurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: NRay Jui <rjui@broadcom.com>
Acked-by: NAntoine Tenart <antoine.tenart@free-electrons.com>
Acked-by: NHongzhou Yang <hongzhou.yang@mediatek.com>
Acked-by: NWei Chen <Wei.Chen@csr.com>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>