iwlwifi: mvm: remove check for vif in iwl_mvm_vif_from_mac80211()

This check is useless, because we would return NULL in that case and
none of the callers actually check that the return value was not NULL
before accessing it.
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>
Link: https://lore.kernel.org/r/iwlwifi.20210802172232.f1c4844a2650.If4dc009e22cda51099a1dc4237d04bf4313055d6@changeidSigned-off-by: Luca Coelho <luciano.coelho@intel.com>

drivers/net/wireless/intel/iwlwifi/mvm/mvm.h

@@ -431,8 +431,6 @@ struct iwl_mvm_vif {
 static inline struct iwl_mvm_vif *
 iwl_mvm_vif_from_mac80211(struct ieee80211_vif *vif)
 {
-	if (!vif)
-		return NULL;
 	return (void *)vif->drv_priv;
 }