ARM: shmobile: Make r8a7779 INTC irqpin platform data static

The platform data for the INTC irq pin driver
seems to be global symbols, make it static to
allow multi-soc build.

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>