dts: x86: Move ioapic node out of cpu container

The IOAPIC node shouldn't have been in the cpu container, especially
since the cpu container does:

	#address-cells = <1>;
	#size-cells = <0>;

So the reg field of the IOAPIC would be treated as 2 registers instead
of a register and size.  Move IOAPIC node out of the CPU node fixes this
issue.

Signed-off-by: Kumar Gala <kumar.gala@linaro.org>