pinctrl: samsung: Detect and handle unsupported configuration types

This patch modifies the pinctrl-samsung driver to detect when width of a
bit field is set to zero (which means that such configuraton type is not
supported) and return an error instead of trying to modify an inexistent
register.

Signed-off-by: Tomasz Figa <t.figa@samsung.com>
Reviewed-by: Kyungmin Park <kyungmin.park@samsung.com>
Acked-by: Thomas Abraham <thomas.abraham@linaro.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>