[SCTP]: Respect the real chunk length when walking parameters.

When performing bound checks during the parameter processing, we
want to use the real chunk and paramter lengths for bounds instead
of the rounded ones.  This prevents us from potentially walking of
the end if the chunk length was miscalculated.  We still use rounded
lengths when advancing the pointer. This was found during a
conformance test that changed the chunk length without modifying
parameters.

Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: Sridhar Samudrala <sri@us.ibm.com>