Normalize conv2d kernel signature

[chenwhql]

Normalize conv2d kernel signature

规范化Conv2D kernel的参数列表，尽可能与python端对齐，移除无用的参数，调整参数顺序等

The Python API signature of conv2d is as follows:

def conv2d(x,
           weight,
           bias=None,
           stride=1,
           padding=0,
           dilation=1,
           groups=1,
           data_format="NCHW",
           name=None):

[qili93]

LGTM