dbus: Fix qdbusxml2cpp unknown type warnings.

Add direction attributes to args where qdbusxml2cpp was looking for the
incorrect annotation.

src/dbus/org.freedesktop.DBus.ObjectManager.xml

@@ -8,7 +8,7 @@
     </method>
     <signal name="InterfacesAdded">
       <arg name="object" type="o"/>
-      <arg name="interfaces" type="a{sa{sv}}"/>
+      <arg name="interfaces" type="a{sa{sv}}" direction="in"/>
       <annotation name="org.qtproject.QtDBus.QtTypeName.In1" value="InterfacesAndProperties"/>
     </signal>
     <signal name="InterfacesRemoved">

src/dbus/org.mpris.MediaPlayer2.Playlists.xml

@@ -20,7 +20,7 @@
 			<annotation name="org.qtproject.QtDBus.QtTypeName.Out0" value="MprisPlaylistList"/>
 		</method>
 		<signal name='PlaylistChanged'>
-			<arg name='Playlist' type='(oss)' />
+			<arg direction='in' name='Playlist' type='(oss)' />
 			<annotation name="org.qtproject.QtDBus.QtTypeName.In0" value="MprisPlaylist" />
 		</signal>
 		<annotation name="org.qtproject.QtDBus.QtTypeName" value="MaybePlaylist" />

src/dbus/org.mpris.MediaPlayer2.TrackList.xml

@@ -24,7 +24,7 @@
 			<arg name='CurrentTrack' type='o'/>
 		</signal>
 		<signal name='TrackAdded'>
-      <arg name='Metadata' type='a{sv}'/>
+			<arg direction='in' name='Metadata' type='a{sv}'/>
 			<annotation name="org.qtproject.QtDBus.QtTypeName.In0" value="TrackMetadata"/>
 			<arg name='AfterTrack' type='o'/>
 		</signal>
@@ -33,7 +33,7 @@
 		</signal>
 		<signal name='TrackMetadataChanged'>
 			<arg name='TrackId' type='o'/>
-      <arg name='Metadata' type='a{sv}'/>
+			<arg direction='in' name='Metadata' type='a{sv}'/>
 			<annotation name="org.qtproject.QtDBus.QtTypeName.In1" value="TrackMetadata"/>
 		</signal>
 		<property name='Tracks' type='ao' access='read'/>