统一 SW_Handler 命名为wch官方sdk标准

[walker2048]

arch/risc-v/risc-v3a/rv32i/gcc/port_s.S board/TencentOS_Tiny_CH32V307_EVB/Startup/startup_ch32v30x.S

以上文件内的SW_handler，与上下文的其他符号命名风格不一致。假如客户自行更新ch32v307的SDK源文件进行替换，编译不会报错，但是因为命名不一致，系统无法正常运行。

[tencent-adm]

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