iwlwifi: improve the flow when a NIC is disconnected

iwlwifi: improve the flow when a NIC is disconnected

When the NIC is disconnected, we just can't do anything
besides seeking for help from the bus driver.  Dumping the
device's memory is not necessary and just bloats the logs
with unusable data.  Moreover, asking mac80211 to restart
the hardware is also useless.  Bypass all this.

Also, use the STATUS_TRANS_DEAD status bit instead of a
bool inside the transport layer. The advantage of this is
that now, the transport and the op_mode can know what is the
situation and bypass the useless recovery steps mentioned
above.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>