dmaengine: Remove memset leftovers

Commit 48a9db46 ("drivers/dma: remove unused support for MEMSET
operations") removed support for the memset operation in dmaengine, but left
the fill_aligned field that was supposed to set the buffer alignment for the
memset operations.

Remove that field too.

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