scsi: storvsc: fix memory leak on ring buffer busy

When storvsc is sending I/O to Hyper-v, it may allocate a bigger buffer
descriptor for large data payload that can't fit into a pre-allocated
buffer descriptor. This bigger buffer is freed on return path.

If I/O request to Hyper-v fails due to ring buffer busy, the storvsc
allocated buffer descriptor should also be freed.

[mkp: applied by hand]

Fixes: be0cf6ca ("scsi: storvsc: Set the tablesize based on the information given by the host")
Cc: <stable@vger.kernel.org>
Signed-off-by: Long Li <longli@microsoft.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/storvsc_drv.c

@@ -1640,6 +1640,8 @@ static int storvsc_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *scmnd)
 	put_cpu();
 
 	if (ret == -EAGAIN) {
+		if (payload_sz > sizeof(cmd_request->mpb))
+			kfree(payload);
 		/* no more space */
 		return SCSI_MLQUEUE_DEVICE_BUSY;
 	}