staging: xgifb: delete command queue selection/init

The driver does not utilize HW command queue in any way, so the code
can be dropped. The support for the default mode (MMIO) and AGP have
been disabled already anyway.

Signed-off-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>