[Backport][NVFP4] ds4-sm120-* hardcodes Mxfp4MoEMethod — DeepSeek-V4-Flash-NVFP4 fails to load on SM120 (works via ModelOpt→Marlin)

[Backport][NVFP4] ds4-sm120-* hardcodes Mxfp4MoEMethod — DeepSeek-V4-Flash-NVFP4 fails to load on SM120 (works via ModelOpt→Marlin) #37