fix dtype checking for softmax (#51929)

Author: zhangting2020

python/paddle/nn/functional/activation.py

@@ -1110,15 +1110,15 @@ def softmax(x, axis=-1, dtype=None, name=None):
         use_cudnn = True
         if dtype is None:
             check_variable_and_dtype(
-                x, 'x', ['float16', 'float32', 'float64'], 'softmax'
+                x, 'x', ['float16', 'bfloat16', 'float32', 'float64'], 'softmax'
             )
         else:
             check_dtype(
                 dtype,
                 'dtype',
-                ['float32', 'float64'],
+                ['float16', 'bfloat16', 'float32', 'float64'],
                 'softmax',
-                'If dtype is not None, it only support float32 or float64.',
+                'If dtype is not None, it only support float16, bfloat16, float32 or float64.',
             )
 
         helper = LayerHelper("softmax", **locals())

python/paddle/nn/layer/activation.py

@@ -1324,7 +1324,7 @@ def __init__(self, axis=-1, name=None):
         self._name = name
 
     def forward(self, x):
-        return F.softmax(x, self._axis, self._dtype, self._name)
+        return F.softmax(x, self._axis, name=self._name)
 
     def extra_repr(self):
         name_str = ', name={}'.format(self._name) if self._name else ''