dmaengine: altera: fix response FIFO emptying

dmaengine: altera: fix response FIFO emptying

Commit 6084fc2ec478 ("dmaengine: altera: Use macros instead of structs
to describe the registers") introduced a minus sign before a register
offset.

This leads to soft-locks of the DMA controller, since reading the last
status byte is required to pop the response from the FIFO. Failing to
do so will lead to a full FIFO, which means that the DMA controller
will stop processing descriptors.

Signed-off-by: Sylvain Lesne <[email protected]>
Reviewed-by: Stefan Roese <[email protected]>
Signed-off-by: Vinod Koul <[email protected]>