dmaengine: fsl-edma: fix calculation of remaining bytes

If the current transfer control descriptor (TCD) was not yet started,
the address will be the same as the initial address. Hence test if the
current address is less than or equal to the start address of each TCD.

Signed-off-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>