iwlwifi: mvm: fix the keyidx assignment

Fixes an issue that smatch pointed out:

  1118
  1119          key_flags = cpu_to_le16(keyconf->keyidx &  STA_KEY_FLG_KEYID_MSK);
                                        ^^^^^^^^^^^^^^^
This is s8.
                                                          ^^^^^^^^^^^^^^^^^^^^^
STA_KEY_FLG_KEYID_MSK is 0x300.

The result after the bitwise AND is always zero because 0xff & 0x300.
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

drivers/net/wireless/iwlwifi/mvm/sta.c

@@ -1116,7 +1116,8 @@ int iwl_mvm_remove_sta_key(struct iwl_mvm *mvm,
 	if (WARN_ON_ONCE(mvm_sta->vif != vif))
 		return -EINVAL;
 
-	key_flags = cpu_to_le16(keyconf->keyidx & STA_KEY_FLG_KEYID_MSK);
+	key_flags = cpu_to_le16((keyconf->keyidx << STA_KEY_FLG_KEYID_POS) &
+				 STA_KEY_FLG_KEYID_MSK);
 	key_flags |= cpu_to_le16(STA_KEY_FLG_NO_ENC | STA_KEY_FLG_WEP_KEY_MAP);
 	key_flags |= cpu_to_le16(STA_KEY_NOT_VALID);