arm64: dts: uniphier: remove unnecessary interrupt-parent

These were added to make the ARM64 branch self-contained because
updates for ARM and ARM64 are supposed to be sent as separate
pull requests.

Now, they were merged together in Linus' tree and interrupt-parent
from the arch/arm/boot/dts/uniphier-support-card.dtsi is visible from
ARM64 DT files by the cross-arch reference.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>