* grub-core/loader/i386/linux.c (grub_linux_setup_video): Use
grub_video_get_driver_id and variable gfxpayloadforcelfb to
fill have_vga.
(grub_linux_boot): Rely on grub_linux_setup_video to fill have_vga and
shift params->lfb_size.
* include/grub/i386/linux.h: Make an enume out of have_vga values.
