contiki/sky: remove useless 'ssize_t' definition config-sky only defines ssize_t which is unused. There is no more platform-specific headers, so remove the comment. Change-Id: I6aea9f21fe1cb4109cfa7d2f6d8b42dcbc3b85b7 Signed-off-by: Gaëtan Harter <gaetan.harter@inria.fr>