dmaengine: idxd: have command status always set

The cached command status is only set when the write back status is
is passed in. Move the variable set outside of the check so it is
always set.

Fixes: 0d5c10b4

 ("dmaengine: idxd: add work queue drain support")
Reported-by: Ramesh Thomas <ramesh.thomas@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/162274329740.1822314.3443875665504707588.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>