[SCTP]: Fix ia64 NaT consumption fault with sctp_sideffect commands.

On ia64, it is possible to get NaT Consumption Fault and a kernel panic
when initializing sctp sideeffect commands arguments.  The union
sctp_arg_t contains different sized elements and when loading a smaller
sized element (32 or 16 bits), it is possible for a speculative load to
fail and result in a NaT bit set which causes a kernel crash.  The easy
way to get around it is to load the largerst member of the union.

Signed-off-by: Vladislav Yasevich <vladislav.yasevich@hp.com>
Signed-off-by: Sridhar Samudrala <sri@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>