* util/i386/pc/grub-mkimage.c (generate_image): If we included a drive
in our prefix, set install_{dos,bsd}_part = -2 to indicate this can be
skipped later.
(main): If a memdisk was requested, add "(memdisk)" drive explicitly to
the beginning of the prefix.
* kern/i386/pc/init.c (make_install_device): Remove memdisk check.
It is assumed that if we have a memdisk, grub-mkimage has set
grub_prefix to include the "(memdisk)" drive in it.