usb: renesas_usbhs: Use dev_of_node macro instead of open coded

This patch uses the dev_of_node macro instead of open coded
to be better.

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>