iwlwifi: fix unused label in iwl_send_cmd_sync

Warning introduced by c847474b7dfdda304d0d8ffcc5a9db546b1cb3e9

iwlwifi: check status before send command

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Wey-Yi Guy <wey-yi.w.guy@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>