ARM: dts: Add missing hwmods property for omap4 dma

On omap4, we are missing a ti,hwmods property for dma that the
that the SoC interconnect code needs.

Note that this will only show up as a bug with "doesn't have
mpu register target base" boot errors when the legacy platform
data is removed.

Cc: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/boot/dts/omap4.dtsi

@@ -312,6 +312,7 @@ sdma: dma-controller@4a056000 {
 			#dma-cells = <1>;
 			dma-channels = <32>;
 			dma-requests = <127>;
+			ti,hwmods = "dma_system";
 		};
 
 		gpio1: gpio@4a310000 {