ARM: dts: keystone: Add aliases for SPI nodes

Add aliases for SPI nodes, this is required to probe the SPI devices in
U-Boot.

Signed-off-by: Vignesh R <vigneshr@ti.com>
Signed-off-by: Santosh Shilimkar <ssantosh@kernel.org>

arch/arm/boot/dts/keystone.dtsi

@@ -20,6 +20,9 @@
 
 	aliases {
 		serial0	= &uart0;
+		spi0 = &spi0;
+		spi1 = &spi1;
+		spi2 = &spi2;
 	};
 
 	memory {