ARM: dts: r9a06g032: Correct GIC compatible value order

According to commit 61efb56e ("dt-bindings: arm: gic: Allow
combining arm,gic-400 compatible strings"), "arm,gic-400" should be
listed first.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Link: https://lore.kernel.org/r/20200519095431.5650-1-geert+renesas@glider.be