iwlwifi: check the HW when a queue is stuck

Add more information when a queue is stuck and actually get
information from the scheduler instead of looking at internal
variables.

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>