sw64: optimize single float load store instruction emulation

Sunway inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I56OLG



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Use instructions instead of manual calculation to move data between
integer register and floating point register to improve performance.

Signed-off-by: Mao Minkai <maominkai@wxiat.com>
Reviewed-by: He Sheng <hesheng@wxiat.com>
Signed-off-by: Gu Zitao <guzitao@wxiat.com>