[Bugfix]Change clip_grad_norm_fp8 to clip_grad_norm_fp32 (#97)

**Description**
Description
The function name of clip_grad_norm_fp8 in megatron/init.py is wrong. It
should be clip_grad_norm_fp32. The gpt3 example can not run successfully
without this PR merged.

msamp/megatron/__init__.py

@@ -3,7 +3,7 @@
 
 """Expose the interface of MS-AMP megatron package."""
 
-from msamp.megatron.optimizer.clip_grads import clip_grad_norm_fp8
+from msamp.megatron.optimizer.clip_grads import clip_grad_norm_fp32
 from msamp.megatron.distributed import FP8DistributedDataParallel
 from msamp.common.utils.lazy_import import LazyImport
 
@@ -13,6 +13,6 @@
 FP8DistributedOptimizer = LazyImport('msamp.megatron.optimizer.distrib_optimizer', 'FP8DistributedOptimizer')
 
 __all__ = [
-    'clip_grad_norm_fp8', 'FP8DistributedDataParallel', 'FP8LinearWithGradAccumulationAndAsyncCommunication',
+    'clip_grad_norm_fp32', 'FP8DistributedDataParallel', 'FP8LinearWithGradAccumulationAndAsyncCommunication',
     'FP8DistributedOptimizer'
 ]