SW: provide xserver-xorg-video-intel on GRML_FULL

For unknown reasons xserver-xorg-video-intel suddenly became
only a Recommends instead of a dependency of xserver-xorg-video-all:

| .../xorg (git)-[debian-unstable] % git show af937437
| commit af937437e6e6a6f34ee247ad2f3aefbd91d7444e
| Author: Timo Aaltonen <tjaalton@debian.org>
| Date:   Tue Mar 8 15:07:25 2016 +0200
|
|     Instead of dropping -intel from -video-all demote it to Recommends.

As a result this package was missing on our Grml ISOs.

Closes grml/grml#20

etc/grml/fai/config/package_config/GRML_FULL

@@ -317,6 +317,7 @@ xserver-xorg
 xserver-xorg-core
 xserver-xorg-input-all
 xserver-xorg-video-all
+xserver-xorg-video-intel
 xterm
 
 # x86 hardware support