pinctrl: nsp: remove redundant dev_err call in nsp_pinmux_probe()

There is a error message within devm_ioremap_resource
already, so remove the dev_err call to avoid redundant
error message.

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Acked-by: Ray Jui <ray.jui@broadcom.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>