This patch changes the driver to allocate DMA descriptors when
needed. This stops memory resources to be wasted and letting
them sit idle in the free_list structure when the device doesn't
need it... This also solves the problem, that a driver has to
guess the number of how many descriptors it needs to allocate
in advance. Currently, the dma engine will just fail when put
under load by sata_dwc_460ex.
Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>