amlogic gx: add lima xorg config bydefault

the default system for this image is the odroid c2 and for xorg to
work on it this config is needed ... it is also required for the
other mali 450 soc (s905, s905x, s905w) based devices and the good
thing is that it seems to work fine still for the mali g31 based
systems as well which do not really need this extra config (tested
on sm1)

systems/amlogic_gx/postinstall.sh

@@ -1,5 +1,6 @@
 #!/bin/bash
 
 cp -v etc/X11/xorg.conf.d.samples/11-modesetting.conf etc/X11/xorg.conf.d
+cp -v etc/X11/xorg.conf.d.samples/13-lima-meson.conf etc/X11/xorg.conf.d
 
 cp -v boot/extra/gxl-tv-box-u-boot.bin boot/u-boot.bin