dmaengine: idxd: fix group conf_dev lifetime

Remove devm_* allocation and fix group->conf_dev 'struct device'
lifetime. Address issues flagged by CONFIG_DEBUG_KOBJECT_RELEASE.
Add release functions in order to free the allocated memory at the
group->conf_dev destruction time.

Reported-by: Jason Gunthorpe <jgg@nvidia.com>
Fixes: bfe1d560

 ("dmaengine: idxd: Init and probe for Intel data accelerators")
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/161852987144.2203940.8830315575880047.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>