ARM: shmobile: r8a7779: add irqpin default status on DTSI

r8a7779 INTC needs IRL pin mode settings to determine
behavior of IRQ0 - IRQ3. But it depends on platform.
This patch adds status = "disabled" on r8a7779.dtsi as default

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>