iwlwifi: mvm: take IWL_MVM_REF_UCODE_DOWN before restarting hw

we unref IWL_MVM_REF_UCODE_DOWN on iwl_mvm_restart_complete().

Usually, the restart is initiated by iwl_mvm_nic_restart(),
which takes the reference before restarting the hw.

However, in D3 flow we might call ieee80211_restart_hw()
directly (in case of suspend error and on d3_test-resume),
which without taking the ref first. fix it.

Signed-off-by: Eliad Peller <eliadx.peller@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>