The VBR value needs to be initialized in order for any of the bios
trapping to work, and as we don't do that until slightly later in the
boot process, this has no real chance of working.

The only reason for using this in the past was due to the fact that early
serial initialization wasn't possible, but now that early sh-sci is
supported by everyone, there's no longer any reason to support the
sh_bios hacks in the first place. Given that, we just kill off the
references completely.
Signed-off-by: Paul Mundt <lethal@linux-sh.org>