Add a device node for the DDR3 Bus State Controller (DBSC3).
The DBSC3 is located in the A4S PM domain, which must not be powered
down, else the system will crash.

This has no visible effect for now, as A4S was never turned off anyway
because its child PM domain A3SM contains the CPU core.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>