The sh73a0 INTC can't mask interrupts properly most likely due to a
hardware bug. Set the .control_parent flag to delegate masking to the
parent interrupt controller, like was already done for irqpin1.

Without this, accessing the three-axis digital accelerometer ADXL345
on kzm9g through /dev/input/event1 causes an interrupt storm, which
requires a power-cycle to recover from.

This was inspired by a patch for arch/arm/boot/dts/sh73a0.dtsi from
Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Fixes: 341eb546 ("ARM: shmobile: INTC External IRQ pin driver on sh73a0")
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>