codespell: fix spelling errors picked out by codespell

README.md

include/byteorder.h

include/list.h

lib/cmp_entity.c

lib/cmp_icu.c

lib/cmp_rdcu.c

lib/rdcu_cmd.c

lib/rdcu_ctrl.c

lib/rdcu_pkt_to_file.c

lib/rdcu_rmap.c

lib/rmap.c

test/cmp_icu/test_decmp.c