usb: gadget: Remove redundant dev_err call in r8a66597_sudmac_ioremap()

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

Acked-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Felipe Balbi <balbi@ti.com>