usb: gadget: r8a66597-udc: handle sudmac registers with devm_ioremap_resource()

Change the sudmac register handling in the devm_ioremap_resource
to use the devm variant.

Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
Signed-off-by: Felipe Balbi <balbi@ti.com>