!8419 add reg for pad fp16 to save time

From: @zhaozhenlong
Reviewed-by: @zhang_xue_tong,@zhanghaibo5
Signed-off-by: @zhang_xue_tong

mindspore/lite/src/runtime/kernel/arm/fp16/pad_fp16.cc

@@ -110,4 +110,5 @@ kernel::LiteKernel *CpuPadFp16KernelCreator(const std::vector<lite::Tensor *> &i
   }
   return kernel;
 }
+REG_KERNEL(kCPU, kNumberTypeFloat16, PrimitiveType_Pad, CpuPadFp16KernelCreator)
 }  // namespace mindspore::kernel