backend: gl: don't force fbconfig info on to heap

It's fairly small, so it's reasonable to put it on the stack.

Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>

src/render.h

@@ -21,7 +21,7 @@ typedef struct paint {
 	xcb_render_picture_t pict;
 	glx_texture_t *ptex;
 #ifdef CONFIG_OPENGL
-	struct glx_fbconfig_info *fbcfg;
+	struct glx_fbconfig_info fbcfg;
 #endif
 } paint_t;