[SCSI] ibmvfc: Fix DMA mapping leak on memory allocation failure

There is currently a DMA mapping leak that can occur in the ibmvfc
driver if we fail to allocate a scatterlist. Fix this by unmapping
the scatterlist in the failure path. Additionally, only log an error
for a scatterlist allocation failure if the log level is greater
than the default, since this can occur when running Active Memory
Sharing and this is not considered an error.

Signed-off-by: Brian King <[e-mail]>
Signed-off-by: James Bottomley <[e-mail]>

drivers/scsi/ibmvscsi/ibmvfc.c

···
 					       &evt->ext_list_token);
 
 		if (!evt->ext_list) {
-			scmd_printk(KERN_ERR, scmd, "Can't allocate memory for scatterlist\n");
+			scsi_dma_unmap(scmd);
+			if (vhost->log_level > IBMVFC_DEFAULT_LOG_LEVEL)
+				scmd_printk(KERN_ERR, scmd, "Can't allocate memory for scatterlist\n");
 			return -ENOMEM;
 		}
 	}