iwlwifi: mvm: remove vif_count

We used to count the number of ieee80211_vifs in mvm.
This was needed for the legacy PM API, which is no longer
supported. Remove it.

Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20220517120045.8c91ae023b15.Ia6145e4930b1d28f3fcedc316b4f177295b00557@changeid


Signed-off-by: Johannes Berg <johannes.berg@intel.com>