irqchip/s3c24xx: Fixup IO accessors for big endian

Instead of using the __raw accessors, use the _relaxed versions
to deal with any issues due to endian-ness of the CPU.

Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk>
[jac: reformat subject line, fix commit message typo]
Link: https://lkml.kernel.org/r/1466504432-24187-10-git-send-email-ben.dooks@codethink.co.uk


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