md: Fix apparent cut-and-paste error in super_90_validate

Setting a variable to itself probably wasn't the intention here.

Signed-off-by: Dave Jones <davej@fedoraproject.org>
Signed-off-by: NeilBrown <neilb@suse.de>
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 16b0822..a2678d8 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -1180,7 +1180,7 @@
 			mddev->bitmap_info.offset =
 				mddev->bitmap_info.default_offset;
 			mddev->bitmap_info.space =
-				mddev->bitmap_info.space;
+				mddev->bitmap_info.default_space;
 		}
 
 	} else if (mddev->pers == NULL) {