Make all depth formats texture filterable.

src/libGLESv2/formatutils.cpp

@@ -624,6 +624,7 @@ struct InternalFormatInfo
         formatInfo.mStorageType = storageType;
         formatInfo.mIsDepthRenderable = depthRenderable;
         formatInfo.mIsStencilRenderable = stencilRenderable;
+        formatInfo.mIsTextureFilterable = AlwaysSupported;
         formatInfo.mSupportFunction = supportFunction;
         return formatInfo;
     }