touchscreen: Evaluate %Tp tag only if pointing mode is enabled

Simply knowing that a touchscreen is present isn't that useful for
themes. Having %Tp evaluate as true when in pointing mode and false
in 3x3 mode is better. For example, themes can change their layout
or hide touch UI elements when in 3x3 mode, or show a status icon.

Although a similar effect can be achieved with the %St tag it's
simpler to use %Tp for this purpose -- it can report the current
mode, not just the user preference.

Change-Id: Ie343c105970dca11864fa44c6a091ed8e9e35b3d

apps/gui/skin_engine/skin_tokens.c

@@ -1457,10 +1457,10 @@ const char *get_token_value(struct gui_wps *gwps,
             return NULL;
         case SKIN_TOKEN_HAVE_TOUCH:
 #ifdef HAVE_TOUCHSCREEN
-            return "t";
-#else
-            return NULL;
+            if (touchscreen_get_mode() == TOUCHSCREEN_POINT)
+                return "t";
 #endif
+            return NULL;
 
 #ifdef HAVE_QUICKSCREEN
         case SKIN_TOKEN_TOP_QUICKSETTING_NAME: