ARM: at91/DT: fix SPI compatibility string

In previous version of SPI driver we where using different compatibility stings
for finding SPI features. We are now using the IP revision information.
So we stay with the unique compatibility string for this driver:
"atmel,at91rm9200-spi".
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Tested-by: Wenyou Yang <wenyou.yang@atmel.com>

arch/arm/boot/dts/sama5d3.dtsi

@@ -76,7 +76,7 @@ mmc0: mmc@f0000000 {
 			spi0: spi@f0004000 {
 				#address-cells = <1>;
 				#size-cells = <0>;
-				compatible = "atmel,at91sam9x5-spi";
+				compatible = "atmel,at91rm9200-spi";
 				reg = <0xf0004000 0x100>;
 				interrupts = <24 IRQ_TYPE_LEVEL_HIGH 3>;
 				cs-gpios = <&pioD 13 0
@@ -204,7 +204,7 @@ mmc2: mmc@f8004000 {
 			spi1: spi@f8008000 {
 				#address-cells = <1>;
 				#size-cells = <0>;
-				compatible = "atmel,at91sam9x5-spi";
+				compatible = "atmel,at91rm9200-spi";
 				reg = <0xf8008000 0x100>;
 				interrupts = <25 IRQ_TYPE_LEVEL_HIGH 3>;
 				cs-gpios = <&pioC 25 0