usb: ohci-ep93xx: use devm_ioremap_resource()

Use devm_ioremap_resource() to make the code a bit cleaner and
simpler.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Cc: Lennert Buytenhek <kernel@wantstofly.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>