sh: Consolidate the sh_bios earlyprintk code.

Now that the sh-sci earlyprintk is taken care of by the sh-sci driver
directly, there's no longer any reason for having a split-out
early_printk framework. sh_bios is the only other thing that uses it, so
we just migrate the leftovers in to there. As it's possible to have
multiple early_param()'s for the same string, there's not much point in
having this split out anymore anyways, particularly since the sh_bios
dependencies are still special-cased within sh-sci itself.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>