fix elewise add precision error

metal/paddle-mobile-demo/paddle-mobile-demo/Net/Net.swift

@@ -45,7 +45,6 @@ protocol Net {
 }
 
 extension Net {
-  
   mutating func load() throws {
     let queue = MetalHelper.shared.queue
     let loader = Loader<Float32>.init()

metal/paddle-mobile/paddle-mobile/Operators/Kernels/ElementwiseAddKernel.swift

@@ -27,7 +27,7 @@ struct ElementwiseAddMetalParam {
 class ElementwiseAddKernel<P: PrecisionType>: Kernel, Computable {
   required init(device: MTLDevice, param: ElementwiseAddParam<P>) {
     super.init(device: device, inFunctionName: "elementwise_add")
-    param.output.initTexture(device: device, inTranspose: param.inputX.transpose)
+    param.output.initTexture(device: device, inTranspose: param.inputX.transpose, computePrecision: computePrecision)
   }
   
   func compute(commandBuffer: MTLCommandBuffer, param: ElementwiseAddParam<P>) throws {