The talitos driver use two dma_map_sg path
according to SG are chained or not.
Since dma_map_sg can handle both case, clean the code with all
references to sg chained.

Thus removing talitos_map_sg, talitos_unmap_sg_chain
and sg_count functions.
Signed-off-by: LABBE Corentin <clabbe.montjoie@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>