sw64: access IO space with readX/writeX

Sunway inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5G5YB



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It's more standard to access IO registers by calling readX/writeX
interfaces. In addition, the code is easier to maintain.

Signed-off-by: He Sheng <hesheng@wxiat.com>

Signed-off-by: Gu Zitao <guzitao@wxiat.com>