staging: xgifb coding style cleanup

This fixes "missing a blank line after declaration" warnings from
checkpatch.pl for driver xgifb. The driver has no remaining errors or
warnings from checkpatch.pl

Signed-off-by: Vitor Braga <vitorpybraga@gmail.com>
Reviewed-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>