iwlwifi: mei: clear the ownership when the driver goes down

When the driver is unregistered, CSME will take ownership on the
device. Reflect this in the iwlmei object so that we will remember
to re-ask for ownership when the driver will register again.

Not doing so will cause CSME not to give the host ownership and
we will see the following error message when trying to bring up
the interface:

iwlwifi 0000:a9:00.0: iwl_pcie_prepare_card_hw iwl_trans_prepare_card_hw enter
iwlwifi 0000:a9:00.0: iwl_pcie_set_hw_ready hardware not ready
iwlwifi 0000:a9:00.0: iwl_pcie_set_hw_ready hardware not ready
iwlwifi 0000:a9:00.0: iwl_pcie_prepare_card_hw Couldn't prepare the card but SAP is connected
iwlwifi 0000:a9:00.0: Error while preparing HW: -16

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20211220142940.c7bb5b7644df.I48498d9fd6e3959562205af67aa5f1a822eb762d@changeid
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>