ARM: dts: porter: Add compatible property to "partitions" node

As of commit e488ca9f8d4f62c2 ("doc: dt: mtd: partitions: add compatible
property to "partitions" node"), the "partitions" subnode of an SPI
FLASH device node must have a compatible property. The partitions are no
longer detected if it is not present.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

arch/arm/boot/dts/r8a7791-porter.dts

@@ -200,6 +200,7 @@
 		m25p,fast-read;
 
 		partitions {
+			compatible = "fixed-partitions";
 			#address-cells = <1>;
 			#size-cells = <1>;