Convert the fp16_params to group of parameters (#1651)
* convert the fp16_params to group of parameters
* fix typo
* check the type of fp16_params
* fix issue when fp16_param_groups is None
Co-authored-by: Jeff Rasley <jerasley@microsoft.com>
Co-authored-by: Olatunji Ruwase <olruwase@microsoft.com>
