The qce 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 qce_mapsg, qce_unmapsg and qce_countsg functions.
Signed-off-by: NLABBE Corentin <clabbe.montjoie@gmail.com>
Signed-off-by: NHerbert Xu <herbert@gondor.apana.org.au>