ARM: dts: Add missing dma hwmod property for omap5

On omap5 we're missing the dma "ti,hwmods" property 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>