ARM: shmobile: sh73a0 dtsi: Set control-parent for all irqpin nodes

The sh73a0 INTC can't mask interrupts properly most likely due to a
hardware bug. Set the control-parent property to delegate masking to the
parent interrupt controller.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>