Fixed setting the layer drawable size

Without this change the drawable had a size of 0 and the metal renderer asserted because the projection matrix wasn't set.

src/video/uikit/SDL_uikitmetalview.m

@@ -60,7 +60,14 @@
 /* Set the size of the metal drawables when the view is resized. */
 - (void)layoutSubviews
 {
+    CGSize bounds;
+
     [super layoutSubviews];
+
+    bounds = [self bounds].size;
+    bounds.width *= self.layer.contentsScale;
+    bounds.height *= self.layer.contentsScale;
+    ((CAMetalLayer *) self.layer).drawableSize = bounds;
 }
 
 @end