dmaengine: idxd: sysfs input of wq incorrect wq type should return error

Currently when inputing an unrecognized wq type, we set the wq type to
"none". It really should return error and not change the existing wq type
that's in the kernel.

Fixes: c52ca478

 ("dmaengine: idxd: add configuration component of driver")
Reported-by: Yixin Zhang <yixin.zhang@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/158213304803.2290.13336343633425868211.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>