dma: edma: Setup parameters to DMA MAX_NR_SG at a time

Changes are made here for configuring existing parameters to support
DMA'ing them out in batches as needed.

Also allocate as many as slots as needed by the SG list, but not more
than MAX_NR_SG. Then these slots will be reused accordingly.
For ex, if MAX_NR_SG=10, and number of SG entries is 40, still only
10 slots will be allocated to DMA the entire SG list of size 40.

Also enable TC interrupts for slots that are a last in a current
iteration, or that fall on a MAX_NR_SG boundary.

Signed-off-by: Joel Fernandes <joelf@ti.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>