sx.c: avoid referencing freed memory if copy_from_user() fails

The "break" would just result in reusing a free'd pointer.  I don't have
the cards myself to test it though.  :/

Signed-off-by: Dan Carpenter <error27@gmail.com>
Cc: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>