sctp: Turn the enum socket options into defines

Recent attempt to remove deprecated socket options demonstrated
that removing options from the enum space will have severe
binary compatibility issues.  The reason is that it changes
the subsequent enum space and causes option values to be redefined.
To solve this, and to get rid of the ugly double statements for
every option, we simply convert to the #define scheme.

Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>