sh: remove consistent alloc stuff from the machine vector

Now with the voyagergx cruft gone and the dreamcast using declared
coherent memory for pci there are no users of the consistent alloc and
free functions pointers in the machine vector.

So this little patch simply removes these function pointers from the macvec.

Signed-off-by: Magnus Damm <damm@igel.co.jp>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>