ARM: shmobile: armadillo800eva: Use DT for GIC

Current Armadillo800eva is using DT booting,
and r8a7740.dtsi already has GIC settings.

So, we can remove the C version of the GIC setup code,
instead rely on GIC information provided by DT.

This patch removes r8a7740_init_irq() which has
no user any more

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Acked-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>