pinctrl: spacemit: return -ENOTSUPP for unsupported pin configurations

pinctrl: spacemit: return -ENOTSUPP for unsupported pin configurations

Return -ENOTSUPP instead of -EINVAL when encountering unsupported pin
configuration parameters. This is more logical and allows the GPIO
subsystem to gracefully handle unsupported parameters via functions like
gpio_set_config_with_argument_optional(), which specifically ignores
-ENOTSUPP but treats others as failure.

Signed-off-by: Junhui Liu <junhui.liu@pigmoral.tech>
Reviewed-by: Anand Moon <linux.amoon@gmail.com>
Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
Reviewed-by: Yixun Lan <dlan@kernel.org>
Signed-off-by: Linus Walleij <linusw@kernel.org>