staging: xgifb: Update TODO

There's no more printk abuse, it's been sorted out in
44881066 ("Staging: xgifb: Remove printk usage.")

Extra ifdefs have been fixed too, mostly in
800d67cf ("staging: xgifb: eliminate #ifdef Tap4"),
c39aada6 ("staging: xgifb: eliminate #ifdef XGIFB_PAN"),
fa4c212f ("staging: xgifb: delete unused definitions"),
5c167b30 ("staging: xgifb: eliminate #ifdef NewScratch"),
f0590773 ("Staging: xgifb: Remove #ifdef MODULE") and more.

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>