arch_interface.h is for architecture and should not be
under sys/. So move it under include/zephyr/arch/.
Signed-off-by: Daniel Leung <daniel.leung@intel.com>
z_xtensa_dump_stack() and z_xtensa_exccause() are both arch
internal functions that should not be exposed in public API.
Signed-off-by: Daniel Leung <daniel.leung@intel.com>