Renesas RZ/N1 SPI Controller

This controller is based on the Synopsys DW Synchronous Serial Interface and
inherits all properties defined in snps,dw-apb-ssi.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-spi", "renesas,rzn1-spi"
   "renesas,r9a06g033-spi", "renesas,rzn1-spi"