dmaengine: idxd: use ida for device instance enumeration

The idr is only used for an device id, never to lookup context from that
id. Switch to plain ida.

Fixes: bfe1d560

 ("dmaengine: idxd: Init and probe for Intel data accelerators")
Reported-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/161852984730.2203940.15032482460902003819.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>