use_dma was always "1" even if the CPU does not support DMA

Tested on AT91SAM9261EK by Jean-Christophe PLAGNIOL-VILLARD
Reported-by: NJean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Signed-off-by: NHong Xu <hong.xu@atmel.com>
Signed-off-by: NArtem Bityutskiy <Artem.Bityutskiy@nokia.com>