dmaengine: mv_xor: remove mv_xor_chan->current_type field

Since commit 3e4f52e2 ("dma: mv_xor: Simplify the DMA_MEMCPY
operation"), this field is no longer used, so get rid of it.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Reviewed-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>