dmaengine: idxd: add missing dsa driver unregister

The idxd_unregister_driver() has never been called for the idxd driver upon
removal. Add fix to call unregister driver on module removal.

Fixes: c52ca478 ("dmaengine: idxd: add configuration component of driver")
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/161947994449.1053102.13189942817915448216.stgit@djiang5-desk3.ch.intel.comSigned-off-by: Vinod Koul <vkoul@kernel.org>

drivers/dma/idxd/init.c

@@ -788,6 +788,7 @@ module_init(idxd_init_module);
 
 static void __exit idxd_exit_module(void)
 {
+	idxd_unregister_driver();
 	pci_unregister_driver(&idxd_pci_driver);
 	idxd_cdev_remove();
 	idxd_unregister_bus_type();