dmaengine: idxd: fix wq slot allocation index check

The sbitmap wait and allocate routine checks the index that is returned
from sbitmap_queue_get(). It should be idxd >= 0 as 0 is also a valid
index. This fixes issue where submission path hangs when WQ size is 1.

Fixes: 0705107f ("dmaengine: idxd: move submission to sbitmap_queue")
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/162697645067.3478714.506720687816951762.stgit@djiang5-desk3.ch.intel.comSigned-off-by: Vinod Koul <vkoul@kernel.org>

drivers/dma/idxd/submit.c

@@ -59,7 +59,7 @@ struct idxd_desc *idxd_alloc_desc(struct idxd_wq *wq, enum idxd_op_type optype)
 		if (signal_pending_state(TASK_INTERRUPTIBLE, current))
 			break;
 		idx = sbitmap_queue_get(sbq, &cpu);
-		if (idx > 0)
+		if (idx >= 0)
 			break;
 		schedule();
 	}