clk: ti: am335x: remove unecessary cpu0 clk node

cpu0 clock node has no functionality, since cpufreq-cpu0 is already
capable of picking up the clock from dts.

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