ARM: shmobile: add gic_iid macro for ICCIAR / interrupt ID

R-Car H1 datasheet GIC number is indicating
GIC ICCIAR / interrupt ID number, not SPI number,
but current marzen board code is using gic_spi() with
un-understandable calculation.

This patch adds new gic_iid() macro which means
ICCIAR / interrupt ID, and used the number
currently written on datasheet.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
[ horms+renesas@verge.net.au: Split board-marzen.c portion into a separate patch ]
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>