LockScreen: Support entering the password from the physical keyboard, without flicking

Always get the focus, if the password changes, ensure we show what's
changing.

look-and-feel/contents/lockscreen/Keypad.qml

@@ -114,6 +114,7 @@ Rectangle {
         password: root.password
         previewCharIndex: -2
         pinLabel: qsTr("Enter PIN")
+        onPasswordChanged: keypadRoot.passwordChanged()
         
         onChangePassword: root.password = password
         Binding {

look-and-feel/contents/lockscreen/LockScreen.qml

@@ -278,9 +278,12 @@ PlasmaCore.ColorScope {
 
             Keypad {
                 id: keypad
-                focus: passwordFlickable.contentY === passwordFlickable.columnHeight
+                focus: true
                 swipeProgress: passwordFlickable.contentY / passwordFlickable.columnHeight
                 Layout.fillWidth: true
+                onPasswordChanged: {
+                    passwordFlickable.contentY = passwordFlickable.contentHeight - passwordFlickable.height
+                }
             }
         }
     }