mn10300: move sg_dma_{address,len}() to asm/scatterlist.h

mn10300 was the only architecture where sg_dma_{address,len}() were not
in asm/scatterlist.h, and it's not a big surprise that this caused a
compile error somewhere:

/home/bunk/linux/kernel-2.6/git/linux-2.6/drivers/media/video/videobuf-dma-sg.c: In function `videobuf_dma_map':
/home/bunk/linux/kernel-2.6/git/linux-2.6/drivers/media/video/videobuf-dma-sg.c:238: error: implicit declaration of function 'sg_dma_address'

Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Adrian Bunk <bunk@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>