x11: Normalize x11xinput2 touch x to be 1.0 at width (thanks, Zach!).

"Applications (such as SDL's testgesture) do "event.tfinger.x * window_width"
to find window coord. Currently the X11 XInput2 backend expects application
to do "event.tfinger.x * (window_width-1)" instead.

X11 XInput2 touch events are normalized so x is 1.0 at "width - 1" but other
SDL backends appear to have x be 1.0 at "width". Same issue for touch event
y with regards to height."

Fixes Bugzilla #4183.

src/video/x11/SDL_x11xinput2.c

@@ -83,16 +83,8 @@ xinput2_normalize_touch_coordinates(SDL_VideoData *videodata, Window window,
     for (i = 0; i < videodata->numwindows; i++) {
         SDL_WindowData *d = videodata->windowlist[i];
         if (d->xwindow == window) {
-            if (d->window->w == 1) {
-                *out_x = 0.5f;
-            } else {
-                *out_x = in_x / (d->window->w - 1);
-            }
-            if (d->window->h == 1) {
-                *out_y = 0.5f;
-            } else {
-                *out_y = in_y / (d->window->h - 1);
-            }
+            *out_x = in_x / d->window->w;
+            *out_y = in_y / d->window->h;
             return;
         }
     }