ARM: OMAP3: Use a single clock for both L3 and L4 DSS interface clocks

Both DSS L3 and L4 interface clocks are controlled by the same bit.
Just use a single clock node to control them, and rename it to dss_ick
as is done for 24xx.

Signed-off-by: Kevin Hilman <khilman@mvista.com>
Acked-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>