rotation: Add rotation to psplash and fbcon
Add rotation to the fbcon and thus the kernel boot logo and the bootsplash program psplash.
Refactor the G&F XML reading functions to the gf-functions shell script that can be sourced. This is also used in the gf-prepare-kernel.sh script during installation to get the rotation value of the display.
Use the fbcon:rotate kernel parameter information to rotate the psplash screen using a systemd-environment-generator script.
BCS 746-000418 BCS 746-000419