iwlwifi: trans: prevent tx and cmds during FW error

Stop Tx and commands from arriving to the transport layer when a FW
error has occurred. A HW recovery should take place before. Remove
transport specific checks of the same nature (note that not all
transports were protected).

Signed-off-by: Arik Nemtsov <arik@wizery.com>
Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>