ARM: dts: s5pv210: add interrupt-parent for ohci

The ohci-hcd node has an interrupt number but no interrupt-parent,
leading to a warning with current dtc versions:

arch/arm/boot/dts/s5pv210-aquila.dtb: Warning (interrupts_property): Missing interrupt-parent for /soc/ohci@ec300000
arch/arm/boot/dts/s5pv210-goni.dtb: Warning (interrupts_property): Missing interrupt-parent for /soc/ohci@ec300000
arch/arm/boot/dts/s5pv210-smdkc110.dtb: Warning (interrupts_property): Missing interrupt-parent for /soc/ohci@ec300000
arch/arm/boot/dts/s5pv210-smdkv210.dtb: Warning (interrupts_property): Missing interrupt-parent for /soc/ohci@ec300000
arch/arm/boot/dts/s5pv210-torbreck.dtb: Warning (interrupts_property): Missing interrupt-parent for /soc/ohci@ec300000

As seen from the related exynos dts files, the ohci and ehci controllers
always share one interrupt number, and the number is the same here as
well, so setting the same interrupt-parent is the reasonable solution
here.

Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>