gpu: fix various small things

 * load color values when dialog is actual visible
 * only allow values which are in range (0-255)
 * convert gpu values properly

Signed-off-by: Blechd0se <alex.christ@hotmail.de>
boot: add color control

Saved as a complete string instead of numerical values.

Signed-off-by: Blechd0se <alex.christ@hotmail.de>
memory: add iosched debug options

Just like the cpu scheduler options add a parameter list.
This is just for testing purposes only.

Signed-off-by: Blechd0se <alex.christ@hotmail.de>