ARM: dts: DRA7: change address-cells and size-cells

DRA7 SoC has the capability to support DDR memory upto 4GB. In order to
represent this in memory dt node, the address-cells and size cells
should be 2. So, changing the address-cells and size-cells to 2 and
updating the memory nodes accordingly.

Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>