ARM: dts: vf610: assign oscillator to clock module

The clock controller module (CCM) has several clock inputs, which
are connected to external crystal oscillators. To reflect this,
assign these fixed clocks to the CCM node directly.

This especially resolves initialization order dependencies we had
with the earlier initialization code: When resolving of the fixed
clocks failed in clk-vf610, the code created fixed clocks with a
rate of 0.

Signed-off-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>