vdma: xilinx: Check if the segment list is empty in a descriptor

The segment list in a descriptor should be checked for empty, else
it will try to access invalid address for the first call.  This
patch fixes this issue.

Signed-off-by: Srikanth Thokala <sthokal@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
vdma: xilinx: Allow only one chunk in a line

This patch adds a sanity check to see if frame_size is 1.

Signed-off-by: Srikanth Thokala <sthokal@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
vdma: xilinx: icg should be difference of stride and hsize

This patch modifies the icg field to match the description
as mentioned in the DMA Linux framework.

Signed-off-by: Srikanth Thokala <sthokal@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>