webgpu: Fix the compile error in conv2d_naive shader (#2002)

BUG

When switch to the naive method of conv2d, below error will be met:
Error: Shader compilation failed: file:124: error: 'getX' : no matching overloaded function found.
Error: Shader compilation failed: file:131: error: 'getW' : no matching overloaded function found.

The fixing uses the right get* methods. And uses int instead of uint as the parameter type.

Author: qjia7

tfjs-backend-webgpu/src/kernels/conv2d_naive_webgpu.ts

@@ -44,18 +44,19 @@ export class Conv2DNaiveProgram implements WebGPUProgram {
         () => 'TODO: Dilation is unimplemented');
 
     this.userCode = `
-      float readInp(uint batch, uint row, uint col, uint chan) {
+      float readInp(int batch, int row, int col, int chan) {
         ivec4 coord = ivec4(batch, row, col, chan);
-        return coordIsValid(coord, xShape) ? getX(coord) : 0;
+        return coordIsValid(coord, xShape) ?
+          getX(batch, row, col, chan) : 0;
       }
 
-      float readFilt(uint row, uint col, uint xChannel, uint outChannel) {
-        ivec4 shape = ivec4(filterDims, xShape[3], outShape[3]);
-        return coordIsValid(coord, shape) ? 
+      float readFilt(int row, int col, int xChannel, int outChannel) {
+        ivec4 coord = ivec4(row, col, xChannel, outChannel);
+        return coordIsValid(coord, wShape) ?
           getW(row, col, xChannel, outChannel) : 0;
       }
 
-      void writeResult(uint batch, uint row, uint col, uint chan, float value) {
+      void writeResult(int batch, int row, int col, int chan, float value) {
         ivec4 coord = ivec4(batch, row, col, chan);
         if (coordIsValid(coord, outShape)) {
           setOutput(batch, row, col, chan, value);