Renesas RZ/N1 UART

This controller is based on the Synopsys DesignWare ABP UART and inherits all
properties defined in snps-dw-apb-uart.txt except for the compatible property.

Required properties:
- compatible : The device specific string followed by the generic RZ/N1 string.
   Therefore it must be one of:
   "renesas,r9a06g032-uart", "renesas,rzn1-uart"
   "renesas,r9a06g033-uart", "renesas,rzn1-uart"