dmaengine: idxd: cleanup completion record allocation

According to core-api/dma-api-howto.rst, the address from
dma_alloc_coherent is gauranteed to align to the smallest PAGE_SIZE order.
That supercedes the 64B/32B alignment requirement of the completion record.
Remove alignment adjustment code.

Tested-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/163517396063.3484297.7494385225280705372.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>