[NET]: Make sure ctl buffer is aligned properly in sys_sendmsg().

It's on the stack and declared as "unsigned char[]", but pointers
and similar can be in here thus we need to give it an explicit
alignment attribute.

Signed-off-by: Alex Williamson <alex.williamson@hp.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>