[SCSI] scsi_debug: prohibit scsi_debug_unmap_granularity == scsi_debug_unmap_alignment

scsi_debug prohibits setting scsi_debug_unmap_alignment to be greater
than scsi_debug_unmap_granularity.  But setting them to be the same value
is not prohibited.  In this case, the only difference with
scsi_debug_unmap_alignment == 0 is the logical blocks from 0 to
scsi_debug_unmap_alignment - 1 cannot be unmapped.  But the difference is
not properly handled in the current code.

So this prohibits such unusual setting.
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Acked-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>

drivers/scsi/scsi_debug.c

@@ -3413,9 +3413,10 @@ static int __init scsi_debug_init(void)
 			clamp(scsi_debug_unmap_granularity, 1U, 0xffffffffU);
 
 		if (scsi_debug_unmap_alignment &&
-		    scsi_debug_unmap_granularity < scsi_debug_unmap_alignment) {
+		    scsi_debug_unmap_granularity <=
+		    scsi_debug_unmap_alignment) {
 			printk(KERN_ERR
-			       "%s: ERR: unmap_granularity < unmap_alignment\n",
+			       "%s: ERR: unmap_granularity <= unmap_alignment\n",
 			       __func__);
 			return -EINVAL;
 		}