Fix and cleanup ssl_cleanup() proto

[michaelortmann]

Found by: michaelortmann Patch by: michaelortmann Fixes:

One-line summary: Fix and cleanup ssl_cleanup() proto

Additional description (if needed): Fix the return type of ssl_cleanup() proto. this function returns void (see tls.c), not int. Such prototypes should be defined in proto.h Found while working on webui.mod. having this separate PR will also make web.ui PR diff smaller.

Test cases demonstrating functionality (if applicable): No functional change