ARM: DTS: dra7/dra7xx-clocks: ATL related changes

Modify the clock nodes for the ATL clocks to use the ATL clock driver to
handle them.

Add the ATL device node at the same time for DRA7.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Acked-by: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>