pinctrl: pass name instead of device to pin_config_*

Obtaining a "struct pinctrl_dev *" is difficult for code not directly
related to the pinctrl subsystem. However, the device name of the pinctrl
device is fairly well known. So, modify pin_config_*() to take the device
name instead of the "struct pinctrl_dev *".

Signed-off-by: Stephen Warren <swarren@nvidia.com>
[rebased on top of refactoring code]
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>