sw64: radeon: correct low-level mmio memset direct calls

Sunway inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I4SPZD


CVE: NA

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Driver codes of the direct calls, via the SIMD-optimized memset and
memcpy functions, may raise dfault under sw64 architecture, so work
around 'memset' references to '_memset_c_io' calls.

Signed-off-by: Gu Zitao <guzitao@wxiat.com> #openEuler_contributor
Signed-off-by: Laibin Qiu <qiulaibin@huawei.com>
Reviewed-by: Hanjun Guo <guohanjun@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>