dmaengine: edma: Create private pset struct

Preparatory patch to support finer grained accounting.

Move the edma_params array out of edma_desc so we can add further per
pset data to it.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
[joelf@ti.com: Fixed up hunk #3 in original patch to apply]
Signed-off-by: Joel Fernandes <joelf@ti.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>