Add fp16 training for ResNeXt101

[huangxu96]

This PR adds fp16 training for ResNeXt101.

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✅ phlrain
✅ DrRyanHuang
✅ zhiqiu
✅ luotao1
✅ zhangting2020
✅ wanghuancoder
❌ chenwhql
❌ FlyingQianMM
❌ huangjun12
❌ jczaja
❌ tianxin
❌ frankwhzhang
❌ ceci3
❌ anpark
❌ LDOUBLEV
❌ xbsu
❌ Xreki
❌ chajchaj
❌ qingqing01
❌ arlesniak
❌ LiuChaoXD
❌ LiuChiachi
❌ ChinaLiuHao
❌ a2824256
❌ shippingwang
❌ shuluoshu
❌ hysunflower
❌ huangxu96

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