SCTP: Add scope_id validation for link-local binds

SCTP currently permits users to bind to link-local addresses,
but doesn't verify that the scope id specified at bind matches
the interface that the address is configured on.  It was report
that this can hang a system.

Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: Adrian Bunk <bunk@stusta.de>