kernel.h implies kernel_structs.h via kernel_includes.h, making
explicit inclusion of kernel_structs.h unnecessary whenever kernel.h
is already included in the same translation unit.
Remove the redundant includes across arch, boards, drivers, kernel,
lib, samples, subsys, and tests trees.
in include/zephyr/kernel_structs.h:
* 2. kernel.h shall imply kernel_structs.h, such that it shall not be
* necessary to include kernel_structs.h explicitly when kernel.h is
* included.
Signed-off-by: Anas Nashif <anas.nashif@intel.com>
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