xa_nn_vec_sigmoid_asym8s_asym8s symble NOT be compiled for HIFI4 target

[hegel-wang]

In the file: tensorflow/lite/micro/kernel/xtensa/logistic.cc, line 88, calling xa_nn_vec_sigmoid_asym8s_asym8s() function.
But in make file: tensorflow/lite/micro/tools/make/ext_libs/xtensa.inc, line 117, it removed xa_nn_activations_asym8_asym8.c containes xa_nn_vec_sigmoid_asym8s_asym8s() define.
So, I do not know whether this file should be included.

[ddavis-2015]

@hegel-wang It seems these lines can be removed from the xtensa.inc file. I just compiled with TARGET=hifi4 (with the lines removed), and saw no errors with a make target of test_kernel_logistic_test.

We will continue to investigate.

[ddavis-2015]

@veblush The exclusion for hifi4 was added in PR#2384 (Jan. 2024) for reasons I am not aware of. Perhaps the original PR author can shed more light on the matter?