Fix wrong idx bug in invertible LayerNormBackward1 (#692)
* fix wrong idx bug in invertible LayerNormBackward1
this index bug cause wrong scale grad
* fix unexpected deletion
* fix idx for LayerNormBackward1_fused_add
* move pos defination in LayerNormBackward1 kernels
* fix format error
Co-authored-by: Reza Yazdani <reyazda@microsoft.com>
