[SCSI] virtio_scsi: fix memory leak on full queue condition.

virtscsi_queuecommand was leaking memory when the virtio queue was full.

Tested: Guest operates correctly even with very small queue sizes, validated
we're not leaking kmalloc-192 sized allocations anymore.

Signed-off-by: Eric Northup <[e-mail]>
Acked-by: Paolo Bonzini <[e-mail]>
Signed-off-by: James Bottomley <[e-mail]>

drivers/scsi/virtio_scsi.c

···
 			      sizeof cmd->req.cmd, sizeof cmd->resp.cmd,
 			      GFP_ATOMIC) >= 0)
 		ret = 0;
+	else
+		mempool_free(cmd, virtscsi_cmd_pool);
 
 out:
 	return ret;