irqchip/exynos-combiner: Fix usage of __raw IO

Fix the use of __raw IO accessors when the readl/writel_relaxed
are better. This should fix issues if the kernel is running as
big endian.

Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
[jac: reformat subject line, fix commit message typo]
Link: https://lkml.kernel.org/r/1466504432-24187-9-git-send-email-ben.dooks@codethink.co.uk


Signed-off-by: Jason Cooper <jason@lakedaemon.net>