Fix issue that user can't edit WFC mode for SIM2

User can't edit WFC mode for SIM2 even if KEY_EDITABLE_WFC_MODE_BOOL for
SIM2 is true. Because WifiCallingSettingsForSub uses subId from
PhoneStateListener. But subId of PhoneStateListener is always default
subId. So, it gets wrong carrier config values.

To fix the problem, WifiCallingSettingsForSub uses its subId.

Bug: 117193148
Test: manual - Checked that WFC preference enable/disable state change
according to the current SIM
Change-Id: I6c8f5c1009c118ae9ca9b6e690d18e11600705eb

src/com/android/settings/wifi/calling/WifiCallingSettingsForSub.java

@@ -112,7 +112,8 @@ public class WifiCallingSettingsForSub extends SettingsPreferenceFragment
             final CarrierConfigManager configManager = (CarrierConfigManager)
                     activity.getSystemService(Context.CARRIER_CONFIG_SERVICE);
             if (configManager != null) {
-                PersistableBundle b = configManager.getConfigForSubId(mSubId);
+                PersistableBundle b =
+                        configManager.getConfigForSubId(WifiCallingSettingsForSub.this.mSubId);
                 if (b != null) {
                     isWfcModeEditable = b.getBoolean(
                             CarrierConfigManager.KEY_EDITABLE_WFC_MODE_BOOL);