target: fix typo Assoication -> Association

Additionally this patch brings proper apply of the designator type.
However, the original code luckily has no bug, because the association
equals to 0.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: James Bottomley <jbottomley@parallels.com>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>