ARM: shmobile: r8a7740 dtsi: Add missing INTCA clock for irqpin module

This clock drives the INTCA irqpin controller modules.
Before, it was assumed enabled by the bootloader or reset state.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: devicetree@vger.kernel.org
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>