wayland: Fix incorrect dereference when sorting icon surfaces

(cherry picked from commit 2f1cf4629c9e76ec2999c8a348e4c55b46c0088d)

src/video/wayland/SDL_waylandmouse.c

@@ -717,8 +717,8 @@ static bool Wayland_GetSystemCursor(SDL_CursorData *cdata, SDL_WaylandCursorStat
 
 static int surface_sort_callback(const void *a, const void *b)
 {
-    SDL_Surface *s1 = *(SDL_Surface **)a;
-    SDL_Surface *s2 = *(SDL_Surface **)b;
+    const SDL_Surface *s1 = *(const SDL_Surface **)a;
+    const SDL_Surface *s2 = *(const SDL_Surface **)b;
 
     return (s1->w * s1->h) <= (s2->w * s2->h) ? -1 : 1;
 }

src/video/wayland/SDL_waylandwindow.c

@@ -3026,8 +3026,8 @@ void Wayland_SetWindowTitle(SDL_VideoDevice *_this, SDL_Window *window)
 
 static int icon_sort_callback(const void *a, const void *b)
 {
-    SDL_Surface *s1 = (SDL_Surface *)a;
-    SDL_Surface *s2 = (SDL_Surface *)b;
+    const SDL_Surface *s1 = *(const SDL_Surface **)a;
+    const SDL_Surface *s2 = *(const SDL_Surface **)b;
 
     return (s1->w * s1->h) <= (s2->w * s2->h) ? -1 : 1;
 }