usb: phy: rcar-usb: Fix comment w.r.t. devm_ioremap_resource

Commit 75096579 ("lib: devres: Introduce devm_ioremap_resource()")
introduced devm_ioremap_resource() and deprecated the use of
devm_request_and_ioremap().

Signed-off-by: Tushar Behera <tushar.behera@linaro.org>
CC: linux-usb@vger.kernel.org
CC: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>