riscv: dts: canaan: Fix SPI FLASH node names

"make dtbs_check":

    arch/riscv/boot/dts/canaan/sipeed_maix_bit.dt.yaml: spi-flash@0: $nodename:0: 'spi-flash@0' does not match '^flash(@.*)?$'
	    From schema: Documentation/devicetree/bindings/mtd/jedec,spi-nor.yaml

Fix this by renaming all SPI FLASH nodes to "flash".
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Tested-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/boot/dts/canaan/sipeed_maix_bit.dts

@@ -199,7 +199,7 @@ slot@0 {
 };
 
 &spi3 {
-	spi-flash@0 {
+	flash@0 {
 		compatible = "jedec,spi-nor";
 		reg = <0>;
 		spi-max-frequency = <50000000>;

arch/riscv/boot/dts/canaan/sipeed_maix_dock.dts

@@ -201,7 +201,7 @@ slot@0 {
 };
 
 &spi3 {
-	spi-flash@0 {
+	flash@0 {
 		compatible = "jedec,spi-nor";
 		reg = <0>;
 		spi-max-frequency = <50000000>;

arch/riscv/boot/dts/canaan/sipeed_maix_go.dts

@@ -209,7 +209,7 @@ slot@0 {
 };
 
 &spi3 {
-	spi-flash@0 {
+	flash@0 {
 		compatible = "jedec,spi-nor";
 		reg = <0>;
 		spi-max-frequency = <50000000>;

arch/riscv/boot/dts/canaan/sipeed_maixduino.dts

@@ -174,7 +174,7 @@ slot@0 {
 };
 
 &spi3 {
-	spi-flash@0 {
+	flash@0 {
 		compatible = "jedec,spi-nor";
 		reg = <0>;
 		spi-max-frequency = <50000000>;