ARM: OMAP3: use DT clock init if DT data is available

OMAP3 platforms support both DT and non-DT boot at the moment, make
the clock init work according to the used setup.

Signed-off-by: Tero Kristo <t-kristo@ti.com>
Tested-by: Nishanth Menon <nm@ti.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>