Fix the missing initialization function

I don't know why was this function removed.

lib/srcnn.lua

@@ -3,6 +3,20 @@ require 'w2nn'
 -- ref: http://arxiv.org/abs/1502.01852
 -- ref: http://arxiv.org/abs/1501.00092
 local srcnn = {}
+
+function nn.SpatialConvolutionMM:reset(stdv)
+   stdv = math.sqrt(2 / ((1.0 + 0.1 * 0.1) * self.kW * self.kH * self.nOutputPlane))
+   self.weight:normal(0, stdv)
+   self.bias:zero()
+end
+if cudnn then
+   function cudnn.SpatialConvolution:reset(stdv)
+      stdv = math.sqrt(2 / ((1.0 + 0.1 * 0.1) * self.kW * self.kH * self.nOutputPlane))
+      self.weight:normal(0, stdv)
+      self.bias:zero()
+   end
+end
+
 function srcnn.channels(model)
    return model:get(model:size() - 1).weight:size(1)
 end