iwlwifi: trigger dump on assert prior to setting the device up

In the regular flow, when we receive an assert, ieee80211_reconfig is
called which reconfig the driver using iwl_mvm_mac_start.
iwl_mvm_mac_start is clearing the restart bit and does dump collection.

Prior to setting the device up, ieee80211_reconfig does not call
iwl_mvm_mac_start since there is nothing to reconfig and we miss the
dump collection of the assert.

solve it by checking the restart bit before we stop the device
and trigger a dump collection in case it is set.

note that we don't need to do it in the fmac case since in fmac
assert flow in iwl_fmac_nic_error we call iwl_fw_dbg_collect_desc
so we can be sure that there will a dump collection in
iwl_fmac_stop_device.

Signed-off-by: Shahar S Matityahu <shahar.s.matityahu@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>