staging: xgifb: Initialize Part0Port

It was left uninitialized, likely overseen, in this commit:
56810a92 ("staging: xgifb: use XGIRegInit()
Avoid copy-paste and use XGIRegInit() to initialize registers addresses.")

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