message: Add exp.h path in the micro Makefile
diff: @@ -400,6 +400,7 @@ tensorflow/lite/kernels/internal/reference/conv.h \
  tensorflow/lite/kernels/internal/reference/depthwiseconv_float.h \
  tensorflow/lite/kernels/internal/reference/depthwiseconv_uint8.h \
  tensorflow/lite/kernels/internal/reference/dequantize.h \
  +tensorflow/lite/kernels/internal/reference/exp.h \
  tensorflow/lite/kernels/internal/reference/floor.h \
  tensorflow/lite/kernels/internal/reference/fully_connected.h \
  tensorflow/lite/kernels/internal/reference/hard_swish.h \
  